Integrate with rules in D8 release

[dlopez-akalam]

Summary:
The wonderful message_notify module integrated with rules will be a nice to have feature, making it usable in many situations without ad-hoc custom development

Solution:
Implement a RulesAction plugin to send the message to its author, as D7 versión does.

[dlopez-akalam]

Here is a PR adding the rules action plugin #84

[dlopez-akalam]

The following patch on rules is needed for this plugin to work. https://www.drupal.org/project/rules/issues/3022250#comment-13688784