refs #25576 [rvktree] restored functionality

See merge request !5

* use HEAD script to keep csp
* add page title and correct heading to improve barf
* improve and sync styles with de_l152 to use package template only

* previous changes made this not function as getRvkData was never using the provided notation
* removed some errant 'debugger' in js script that resides there since 2021

Issue/25351

See merge request !4

* organize imports
* correct php doc for params (better ide autocompletion)

refs 25351 [rvk] updated rvk json retrival

See merge request !3

* replaced file_content_get with proper laminas query
* inplace replaced zend with laminas

refs #23552 [de_l242] modified rvk-tree css to be more specific and only apply to rvk container

See merge request !2

* change headline
* minimize css/js dependency

* set tabindex 0 instead of -1 for nodes
* break search link for smaller screens

* add icons
* handle overflow
* adjust layout

* remove spare dependencies from composer.json
* add important javascript files in templates directoy and register in mixin.config
* refactor rvktree.js
** call only on RVK site by template directly
** add fallback for translationShow variable
* add default url and default rvk sections in Rvk.php
* add Readme

* TODO:
** rename master to main
** add css, icons for plus and minus
** caching
** copy repo to packagist