[5.0] Editor xtd buttons use postMessage()

[Fedik]

Pull Request for Issue # .

Summary of Changes

This is futher join of:

• [5.0] Generic ModalSelect field #40462
• [5.0][RFC] Joomla.Editor and Joomla.EditorButton client side API #40202

In this PR I have add use of postMessage to Article, Module, Fields XTD buttons.

This is backward compatible.

Testing Instructions

Apply patch, run npm install.
Edit article, and use Article, Module, Fields XTD buttons.

Actual result BEFORE applying this Pull Request

All works

Expected result AFTER applying this Pull Request

All works but better

Link to documentations

Please select:

• Documentation link for docs.joomla.org:
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org: Editor and Editor buttons (XTD) plugins Manual#97 Content select in modal Manual#178
• No documentation changes for manual.joomla.org needed

[HLeithner]

for completeness I merge this now for beta1, thanks