💥 Remove :feature category

:feature was a "catch-all" category. Many of its modules fit better in
other categories, so they've been moved:

- feature/debugger -> tools/debugger
- feature/evil -> editor/evil
- feature/eval -> tools/eval
- feature/lookup -> tools/lookup
- feature/snippets -> editor/snippets
- feature/file-templates -> editor/file-templates
- feature/workspaces -> ui/workspaces

More potential changes in the future:

- A new :term category for terminal emulation modules (eshell, term and
  vterm).
- A new :os category for modules dedicated to os-specific functionality.
  The :tools macos module would fit here, but so would modules for nixos
  and arch.
- A new :services category for web-service integration, like wakatime,
  twitter, elfeed, gist and pastebin services.

modules/editor/fold/config.el

@@ -1,6 +1,6 @@
 ;;; editor/fold/config.el -*- lexical-binding: t; -*-
 
-(when (featurep! :feature evil)
+(when (featurep! :editor evil)
   ;; Add vimish-fold, outline-mode & hideshow support to folding commands
   (define-key! 'global
     [remap evil-toggle-fold]   #'+fold/toggle
@@ -57,7 +57,7 @@
 
 
 (def-package! evil-vimish-fold
-  :when (featurep! :feature evil)
+  :when (featurep! :editor evil)
   :commands (evil-vimish-fold/next-fold evil-vimish-fold/previous-fold
              evil-vimish-fold/delete evil-vimish-fold/delete-all
              evil-vimish-fold/create evil-vimish-fold/create-line)