[Feature] Support nerd-icons

[seagle0128]

Thanks for this great package.

Could you please support nerd-icons in lsp-treemacs-themes? I create one as below.

(treemacs-create-theme "lsp-nerd-icons"
           :config
           (progn
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-repo" :face 'nerd-icons-blue))
              :extensions (root))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_boolean" :face 'nerd-icons-lblue))
              :extensions (boolean-data))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_class" :face 'nerd-icons-orange))
              :extensions (class))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_color"))
              :extensions (color-palette))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_constant"))
              :extensions (constant))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_file"))
              :extensions (document))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_misc" :face 'nerd-icons-orange))
              :extensions (enumerator))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_enum_member" :face 'nerd-icons-lblue))
              :extensions (enumitem))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_event" :face 'nerd-icons-orange))
              :extensions (event))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_field" :face 'nerd-icons-lblue))
              :extensions (field))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_misc"))
              :extensions (indexer))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_keyword"))
              :extensions (intellisense-keyword))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_interface" :face 'nerd-icons-lblue))
              :extensions (interface))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_variable" :face 'nerd-icons-lblue))
              :extensions (localvariable))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_method" :face 'nerd-icons-purple))
              :extensions (method))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_namespace" :face 'nerd-icons-lblue))
              :extensions (namespace))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_numeric"))
              :extensions (numeric))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_operator"))
              :extensions (operator))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_property"))
              :extensions (property))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_snippet"))
              :extensions (snippet))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_string"))
              :extensions (string))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_structure" :face 'nerd-icons-orange))
              :extensions (structure))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_snippet"))
              :extensions (template))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-chevron_right" :face 'nerd-icons-dsilver))
              :extensions (collapsed) :fallback "+")
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-chevron_down" :face 'nerd-icons-dsilver))
              :extensions (expanded) :fallback "-")
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-file_binary" :face 'nerd-icons-dsilver))
              :extensions (classfile))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-blue))
              :extensions (default-folder-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-blue))
              :extensions (default-folder))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-green))
              :extensions (default-root-folder-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-green))
              :extensions (default-root-folder))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-file_binary" :face 'nerd-icons-dsilver))
              :extensions ("class"))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-file_zip" :face 'nerd-icons-dsilver))
              :extensions (file-type-jar))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-dsilver))
              :extensions (folder-open))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-dsilver))
              :extensions (folder))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-orange))
              :extensions (folder-type-component-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-orange))
              :extensions (folder-type-component))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-green))
              :extensions (folder-type-library-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-green))
              :extensions (folder-type-library))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-pink))
              :extensions (folder-type-maven-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-pink))
              :extensions (folder-type-maven))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-orange))
              :extensions (folder-type-package-opened))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-orange))
              :extensions (folder-type-package))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-add" :face 'nerd-icons-dsilver))
              :extensions (icon-create))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-list_flat" :face 'nerd-icons-dsilver))
              :extensions (icon-flat))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-symbol_class" :face 'nerd-icons-blue))
              :extensions (icon-hierarchical))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-link" :face 'nerd-icons-dsilver))
              :extensions (icon-link))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-refresh" :face 'nerd-icons-dsilver))
              :extensions (icon-refresh))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-faicon "nf-fa-unlink" :face 'nerd-icons-dsilver))
              :extensions (icon-unlink))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-devicon "nf-dev-java" :face 'nerd-icons-orange))
              :extensions (jar))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-library" :face 'nerd-icons-green))
              :extensions (library))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder_opened" :face 'nerd-icons-lblue))
              :extensions (packagefolder-open))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-folder" :face 'nerd-icons-lblue))
              :extensions (packagefolder))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-archive" :face 'nerd-icons-dsilver))
              :extensions (package))
             (treemacs-create-icon
              :icon (format "%s " (nerd-icons-codicon "nf-cod-repo" :face 'nerd-icons-blue))
              :extensions (java-project))))

Please refer to https://github.com/seagle0128/.emacs.d/blob/6bc1d65dc7c46cc0acbac42d23a9ba0b9b64523b/lisp/init-lsp.el#L321