Atto multilanguage plugin

This plugin will make the creation of multilingual contents on Moodle much more easier with Atto editor.

The plugin is developed to work with Iñaki Arenaza's multilang2 filter, and the idea is based on his plugin for TinyMCE editor.

Current version

The latest release is v1.12 (build 2021063000) for Moodle 3.9, 3.10, 3.11 and 4.0.

The tag 'other' has been added to the list of languages of the Multilang2 button in order to fit with the functionality that the 1.1.1 version of filter_multilang2 implements.

The Privacy Api has been implemented so that this plugin complies with the new General Data Protection Regulation (GDPR), effective as of May 25, 2018.

Added Grunt support files. No we can check Moodle Javascript coding guidelines and minify the plugin code without installing the plugins.
Minor Javascript coding guidelines fix (signalled by the minifier, but ignored by the linter!)

Multiple bug fixes, especially when there were more than one Atto editor in the same page. Closes issues #2, #18, #21.
Multilang tag highlighting 's are now removed/added when switching to/from HTML view, reducing clutter when editing the HTML code.
Cleaned the code to conform to PHP, PHPDoc and Javascript Moodle coding guidelines (all checks pass!)

As mentioned before, filter_multilang2 is required.

Copy repository content in moodleroot/lib/editor/atto/plugins. The following can be omitted:
- tests/ (if you're not going to test it with Behat or PHPUnit)
- .gitmodules
- build.xml
Install the plugin from Moodle.
Go to "Site administration" >> "Plugins" >> "Text editors" >> "Atto HTML editor" >> "Atto toolbar settings", and add multilang2 to the Toolbar config where you prefer. E.g. other = multilang2, ... or multilang2 = multilang2 (see Text editor - Toolbar settings and Text editor - Adding extra buttons for instructions on how to add a plugin button to Atto toolbar.