💥 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/tools/vterm/config.el

@@ -11,7 +11,7 @@
   ;; Automatically kill buffer when vterm exits.
   (add-to-list 'vterm-exit-functions (lambda (buffer) (if buffer (kill-buffer buffer))))
 
-  (when (featurep! :feature evil)
+  (when (featurep! :editor evil)
     (evil-set-initial-state 'vterm-mode 'insert)
     ;; Go back to normal state but don't move cursor backwards. Moving cursor
     ;; backwards is the default Vim behavior but it is not appropriate in some