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/ui/popup/config.el

@@ -156,6 +156,9 @@ prevent the popup(s) from messing up the UI (or vice versa)."
       ;; `help-mode', `helpful-mode'
       ("^\\*[Hh]elp"
        :slot 2 :vslot 2 :size 0.35 :select t)
+      ;; `eww' (and used by dash docsets)
+      ("^\\*eww\\*"
+       :vslot 50 :size 0.35 :select t)
       ;; `Info-mode'
       ("^\\*info\\*$"
        :slot 2 :vslot 2 :size 0.45 :select t)))