💥 Replace core-popup with new feature/popup module

This is a breaking change! Update your :popup settings. Old ones will
throw errors!

Doom's new popup management system casts off its shackles (hur hur) and
replaces them with the monster that is `display-buffer-alist`, and
window parameters.

However, this is highly experimental! Expect edge cases.  Particularly
with org-mode and magit (or anything that does its own window
management).

Relevant to #261, #263, #325

modules/app/twitter/config.el

@@ -16,8 +16,6 @@
         twittering-initial-timeline-spec-string
         '(":home" ":mentions" ":direct_messages"))
 
-  (set! :popup "*twittering-edit*" :size 12 :select t)
-
   (add-hook! twittering-mode
     (setq header-line-format (or (doom-modeline 'twitter) mode-line-format)
           mode-line-format nil))