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/autoload/lookup.el

@@ -63,6 +63,10 @@ properties:
   `(set-lookup-handlers! ,modes ,@plist))
 
 
+;;
+;; Library
+;;
+
 ;; Helpers
 (defun +lookup--online-provider (&optional force-p namespace)
   (let ((key (or namespace major-mode)))
@@ -201,17 +205,18 @@ Goes down a list of possible backends:
 3. Fall back to an online search, with `+lookup/online'"
   (interactive
    (list (+lookup--symbol-or-region)))
-  (cond ((and +lookup-documentation-functions
+  (cond ((null identifier) (user-error "Nothing under point"))
+
+        ((and +lookup-documentation-functions
               (+lookup--jump-to :documentation identifier)))
 
         ((and (featurep! +docsets)
               (or (require 'counsel-dash nil t)
                   (require 'helm-dash nil t))
-              (or (bound-and-true-p counsel-dash-docsets)
-                  (bound-and-true-p helm-dash-docsets))
-              ;; counsel-dash uses helm-dash under the hood
-              (helm-dash-installed-docsets))
-         (+lookup/in-docsets identifier))
+              (let ((docsets (+lookup-docsets-for-buffer)))
+                (when (cl-some #'+lookup-docset-installed-p docsets)
+                  (+lookup/in-docsets identifier docsets)
+                  t))))
 
         ((+lookup/online
           identifier