Clarify `submit_button()` `$type` parameter docs to mention that the value doubles as the CSS class attribute.

See #27070


git-svn-id: https://develop.svn.wordpress.org/trunk@27135 602fd350-edb4-49c9-b593-d223f7449a82
Improve inline documentation for `submit_button()`.

See #27070.


git-svn-id: https://develop.svn.wordpress.org/trunk@27136 602fd350-edb4-49c9-b593-d223f7449a82
Fix docs spacing missed in [27136].

See #27070.


git-svn-id: https://develop.svn.wordpress.org/trunk@27137 602fd350-edb4-49c9-b593-d223f7449a82