[FEATURE] Add pattern attribute to TextfieldViewHelper

In order to allow HTML5 validation, the Textfield ViewHelper needs
"pattern" as an attribute.

Resolves: #62428
Releases: master
Change-Id: Idbb35fafec2220c255e2ae3f82ad30f8fe84133d
Reviewed-on: http://review.typo3.org/35601
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>