💥 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/emacs/eshell/config.el

@@ -81,7 +81,7 @@ You should use `det-eshell-alias!' to change this.")
   (add-hook 'eshell-mode-hook #'smartparens-mode)
 
   ;; Persp-mode/workspaces integration
-  (when (featurep! :feature workspaces)
+  (when (featurep! :ui workspaces)
     (add-hook 'persp-activated-functions #'+eshell|switch-workspace)
     (add-hook 'persp-before-switch-functions #'+eshell|save-workspace))
 
@@ -115,7 +115,7 @@ You should use `det-eshell-alias!' to change this.")
                   +eshell-aliases)))
   (add-hook 'eshell-alias-load-hook #'+eshell|init-aliases)
 
-  (when (featurep! :feature evil +everywhere)
+  (when (featurep! :editor evil +everywhere)
     (add-hook 'eshell-mode-hook #'+eshell|init-evil))
 
   (defun +eshell|init-keymap ()