Releases for Field Group Ajaxified Multipage

Make the module compatible with drupal 9

#3147477: Automated Drupal 9 compatibility fixes
#3226013: Drupal 9 compatible

Added composer.json with field_group as required.
Added test functional and functional with javascript. PHPUnit

* #1972502 Supporting multilevel fieldgroups by @TimBrandin
* #1971780 Undefined index: FIELDNAME locale_field_node_form_submit() by @TimBrandin
* Example module for demonstration and test
* warning when submit button is not inside actions item in form array
* all notices and warnings when using with custom forms fixed. Also incorrect
sorting of custom forms page groups fixed
* #1971878 Undefined index #attributes in field_group_ajaxified_multipage_form_alter @Dustin Bons
* README updated for new hook

* updating readme to covert new changes
* New option "Non Javascript Multistep" for fieldgroup which does not require javascript to work.
It's very useful for debugging purposes or very complex multistep forms.
* partial support for user registration form, works with "Non Javascript Multistep"
option but not yet with ajaxify option
* No longer relies on button's title to determine which button is clicked, button
title can be customized
* Updated README.txt for covering the changes in the previous commit

* some minor bugs fixed