feat(MarkdownBuilder): add AA markdown builder

Author: CarloGauss33

lib/activeadmin_addons/addons/markdown_builder.rb

@@ -0,0 +1,38 @@
+require 'redcarpet'
+
+module ActiveAdminAddons
+  class MarkdownBuilder < CustomBuilder
+    def render
+      return if data.blank?
+
+      Redcarpet::Markdown.new(renderer, extensions).render(@data).html_safe
+    end
+
+    private
+
+    def extensions_default
+      { fenced_code_blocks: true,
+        no_intra_emphasis: true,
+        strikethrough: true,
+        superscript: true }
+    end
+
+    def renderer_options_default
+      { filter_html: true, hard_wrap: true }
+    end
+
+    def extensions
+      @extensions ||= extensions_default.merge(options[:extensions] || {})
+    end
+
+    def render_options
+      @render_options ||= renderer_options_default.merge(options[:render_options] || {})
+    end
+
+    def renderer
+      @renderer ||= Redcarpet::Render::HTML.new(render_options)
+    end
+  end
+end
+
+ActiveAdminAddons::MarkdownBuilder.create_view_methods