💥 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/lookup/packages.el

@@ -0,0 +1,21 @@
+;; -*- no-byte-compile: t; -*-
+;;; tools/lookup/packages.el
+
+;; `dumb-jump' uses the `helm-build-sync-source' macro, but this requires helm
+;; be loaded before it is byte-compiled during installation. To ensure this, we
+;; declare helm before dumb-jump.
+(when (featurep! :completion helm)
+  (package! helm))
+
+;;
+(package! dumb-jump)
+(when (featurep! :completion ivy)
+  (package! ivy-xref))
+(when (featurep! :completion helm)
+  (package! helm-xref))
+
+(when (featurep! +docsets)
+  (when (featurep! :completion helm)
+    (package! helm-dash))
+  (when (featurep! :completion ivy)
+    (package! counsel-dash)))