Typo/style fixes in docs and code comments

Codespell(1)-pointed typos in files listed by `git ls-files`
(sans checkpatch.pl and possibly some others). Removed some
extra spaces. Added a few missing trailing periods.
`Default is ...`.  Added spaces in ' />' where missing
(sans e.g. wayland protocol and t/* files).
Fit some lines in docs/*.scd to 80 colums.

Used git grep commands (to find similar cases):
$ git grep -n '\S/>'
$ git grep -nF '.  '
$ git grep -n '[^\t*'\'',{#]\t'
$ git grep -ni 'default '

No functional change. No change in *.[ch] line numbers.

src/action.c

@@ -145,7 +145,7 @@ struct action_arg_list {
  * Will expand to:
  *
  * enum action_type {
- *	ACTION_TYPE_INVALID,
+ *	ACTION_TYPE_INVALID = 0,
  *	ACTION_TYPE_NONE,
  *	ACTION_TYPE_CLOSE,
  *	ACTION_TYPE_KILL,
@@ -1312,7 +1312,7 @@ run_action(struct view *view, struct action *action,
 
 			/*
 			 * To support only setting one of width/height
-			 * in <action name="ResizeTo" width="" height=""/>
+			 * in <action name="ResizeTo" width="" height="" />
 			 * we fall back to current dimension when unset.
 			 */
 			struct wlr_box box = {