Backport changes from Emacs

Added in this commit:
- 9230953f23 ; Fix typos.

Already done independently:
- 640e52d8fa ; Fix mistakes in 'declare function' forms
- bbf389ea6d Audit quoting the quote character in doc strings
- 19dcb237b5 ; Add 2022 to copyright years.

Not included:
- 49e41991b2 Allow ;;;###autoloading transient-define-prefix
  For stand-alone transient that isn't sufficient to make it
  unnecessary to load the library upfront, but makes it more
  likely that a user thinks it is.  Emacs handles this macro
  in loaddefs-generate--make-autoload.
- 15238e2ed0 Prefer URL commentary header in two files
  I prefer Homepage and use it consistently in all my libraries.

lisp/transient.el

@@ -260,7 +260,7 @@ for infix argument are highlighted when only a long argument
 In the rare case that a short-hand is specified but does not
 match the key binding, then it is highlighted differently.
 
-The highlighting is done using using `transient-mismatched-key'
+The highlighting is done using `transient-mismatched-key'
 and `transient-nonstandard-key'."
   :package-version '(transient . "0.1.0")
   :group 'transient