💥 Refactor add-hook! macro & change arg order

This update may potentially break your usage of add-hook! if you pass
the :local or :append properties to it. This is how they used to work:

  (add-hook! :append 'some-mode-hook #'do-something)

Thsoe properties must now follow the hooks, e.g.

  (add-hook! 'some-mode-hook :append #'do-something)

Other changes:
- Various add-hook calls have been renamed to add-hook! because I
  incorrectly assumed `defun` always returned its definition's symbol,
  when in fact, its return value is "undefined" (so sayeth the
  documentation). This should fix #1597.
- This update adds the ability to add multiple functions to hooks
  without a list:

    (add-hook! 'some-mode-hook
               #'do-something
               #'do-something-else)

- The indentation logic has been changed so that consecutive function
  symbols at indented at the same level as the first argument, but forms
  are indent like a defun.

    (add-hook! 'some-mode-hook
               #'do-something
               #'do-something-else)

    (add-hook! 'some-mode-hook
      (message "Hello"))

modules/lang/idris/config.el

@@ -1,7 +1,7 @@
 ;;; lang/idris/config.el -*- lexical-binding: t; -*-
 
 (after! idris-mode
-  (add-hook! 'idris-mode-hook 'turn-on-idris-simple-indent)
+  (add-hook 'idris-mode-hook #'turn-on-idris-simple-indent)
   (set-repl-handler! 'idris-mode 'idris-pop-to-repl)
   (set-lookup-handlers! 'idris-mode
     :documentation #'idris-docs-at-point