Improvements to apropos and describe-symbol

Patch the apropos button types so they call helpful instead of the
built-in describe functions.  Also add some bindings to apropos-mode-map
so it behaves like other help modes.

Add `doom/describe-symbol` function, which shows documentation for
callable and variable symbols.  If a symbol is both a variable and a
callable, it dispatches to apropos.  This gives a better workflow than
`helpful-symbol`, which annoyingly prompts the user.

Remap `describe-symbol` to `doom/describe-symbol`, and update
`+emacs-lisp-lookup-documentation` to call it also.

core/core-editor.el

@@ -271,13 +271,31 @@ savehist file."
 
 ;; `helpful' --- a better *help* buffer
 (def-package! helpful
-  :defer t
+  :commands (helpful-callable
+             helpful-command
+             helpful-variable
+             helpful-key
+             helpful--read-symbol)
   :init
   (define-key!
     [remap describe-function] #'helpful-callable
     [remap describe-command]  #'helpful-command
     [remap describe-variable] #'helpful-variable
-    [remap describe-key]      #'helpful-key))
+    [remap describe-key]      #'helpful-key
+    [remap describe-symbol]   #'doom/describe-symbol)
+
+  (after! apropos
+    ;; patch apropos buttons to call helpful instead of help
+    (dolist (fun-bt '(apropos-function apropos-macro apropos-command))
+      (button-type-put
+       fun-bt 'action
+       (lambda (button)
+         (helpful-callable (button-get button 'apropos-symbol)))))
+    (dolist (var-bt '(apropos-variable apropos-user-option))
+      (button-type-put
+       var-bt 'action
+       (lambda (button)
+         (helpful-variable (button-get button 'apropos-symbol)))))))
 
 
 (def-package! ws-butler