editor/snippets: expand on snippet commands & keybinds

- Introduces the +snippets/new (SPC s n) command for creating a new
  private snippet
- Introduces the +snippets/new-lias (SPC s N) command for creating a new
  private snippet alias, which will invoke another snippet (you will be
  prompted to select one). This will only work with the emacs-snippets
  library bundled with Doom Emacs, however, as it depends on its API.
- Introduces +snippets/edit (SPC s c) for modifying existing snippets.
  How this differs from yas-visit-snippet-file is it will copy the
  contents of built-in snippets into a buffer primed for your private
  snippets (in DOOMDIR/snippets), while yas-visit-snippet-file will
  simply open the originating snippet.
- Introduces the +snippets/find (SPC s ?),
  +snippets/find-for-current-mode (SPC s /) and
  +snippets/find-private (SPC s f) commands for, respectively, finding a
  snippet file among *all* directories in yas-snippet-dirs, finding a
  snippet for the current major mode (plus parents), and finding a
  snippet from among your private library. This opens built-in snippets
  in read-only mode, but you can press C-c C-e to open it in
  +snippets/edit.

modules/config/default/+evil-bindings.el

@@ -793,14 +793,16 @@
       ;;; <leader> s --- snippets
       (:when (featurep! :editor snippets)
         (:prefix-map ("s" . "snippets")
-          :desc "New snippet"                "n" #'yas-new-snippet
+          :desc "View snippet for mode"      "/" #'+snippets/find-for-current-mode
+          :desc "View snippet (global)"      "?" #'+snippets/find
+          :desc "Edit snippet"               "c" #'+snippet/edit
+          :desc "View private snippet"       "f" #'+snippets/find-private
           :desc "Insert snippet"             "i" #'yas-insert-snippet
-          :desc "Jump to mode snippet"       "/" #'yas-visit-snippet-file
-          :desc "Jump to snippet"            "s" #'+snippets/find-file
-          :desc "Browse snippets"            "S" #'+snippets/browse
+          :desc "New snippet"                "n" #'+snippet/new
+          :desc "New snippet alias"          "N" #'+snippet/new-alias
           :desc "Reload snippets"            "r" #'yas-reload-all
-          :desc "Create temporary snippet"   "c" #'aya-create
-          :desc "Use temporary snippet"      "e" #'aya-expand))
+          :desc "Create temporary snippet"   "s" #'aya-create
+          :desc "Expand temporary snippet"   "e" #'aya-expand))
 
       ;;; <leader> t --- toggle
       (:prefix-map ("t" . "toggle")