Add savefold (#541)

Author: jcs090218

README.org

@@ -536,6 +536,7 @@ Above all, enjoy using Emacs. The community, more than anything, makes Emacs a g
     - [[https://github.com/emacs-tree-sitter/ts-fold][ts-fold]] - Code-folding using tree-sitter.
     - [[https://github.com/emacs-tree-sitter/treesit-fold][treesit-fold]] - Code folding based on the tree-sitter syntax tree, built on top of treesit.el.
     - [[https://github.com/jamescherti/outline-indent.el][outline-indent]] - Fold text based on indentation levels.
+    - [[https://github.com/jcfk/savefold.el][savefold]] - Persistence for various Emacs folding systems.
 
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