feature/lookup: rewrite dash docset integration

+ Uses alist variable to store config, rather than hooks
+ Added check for installed docsets in +lookup/documentation
+ Set docsets for various language modules (c-mode, c++-mode, css-mode,
  scss-mode, sass-mode, web-mode, go-mode, racket-mode, emacs-lisp-mode,
  js2-mode, rjsx-mode, typescript-mode, rust-mode, and php-mode)
+ Made *eww* popups for dash docsets larger
+ Renamed set-docset! => set-docsets! (set-docset! is aliased to
  set-docsets!)
+ New +lookup/install-docset alias

modules/feature/lookup/config.el

@@ -120,8 +120,8 @@ argument: the identifier at point.")
 
 ;; Both packages depend on helm-dash, for now
 (def-package! helm-dash
-  :defer t
   :when (featurep! +docsets)
+  :defer t
   :init
   (setq helm-dash-enable-debugging doom-debug-mode
         helm-dash-browser-func #'eww)