feat!(cli): load project .doomrc instead of ci.el

BREAKING CHANGE: Before, 'doom ci' would load
$GIT_WORKING_TREE/.github/ci.el, to give users/projects an opportunity
to provide project-local configuration for bin/doom (mainly for CI/CD).
Now, this ci.el file is no longer loaded and instead, *all* bin/doom
sessions will walk up the file tree and load the first .doomrc it finds.

This gives bin/doom users a more general place configure all of its
commands, and not just 'doom ci' commands.

Extras:
- Adds .doomrc to auto-mode-alist (so that it starts in
  emacs-lisp-mode).

lisp/doom-start.el

@@ -143,7 +143,8 @@ If RETURN-P, return the message as a string instead of displaying it."
                      (float-time (time-subtract (current-time) before-init-time))))))
 
 ;; Add support for additional file extensions.
-(dolist (entry '(("/LICENSE\\'" . text-mode)
+(dolist (entry '(("/\\.doomrc\\'" . emacs-lisp-mode)
+                 ("/LICENSE\\'" . text-mode)
                  ("\\.log\\'" . text-mode)
                  ("rc\\'" . conf-mode)
                  ("\\.\\(?:hex\\|nes\\)\\'" . hexl-mode)))