Tinymce html5 containers

[brianteeman]

This PR adds the ability to mark your content with aside, article and section which are important landmarks that a content author may wish to use.

To test simply apply this PR and then you will find the new options as shown below.

You can then apply these containers to any blocks of content and verify that it worked either by toggling the editor or by displaying visual characters in tinymce from the toolbar button.

[dgrammatiko]

Shouldn't those be in the Block dropdown? Also, capitalise the first letter?

[brianteeman]

As they are bigger than blocks I thought it best to place them in their own menu group. Containers can contain blocks.

I chose not to capitalise on purpose (after quite a bit of thought) as they are the name of the tags and not a descriptor of the tag (eg Paragraph for p)

[infograf768]

The word Containers is not included in TinyMce lang files (see https://github.com/joomla/joomla-cms/blob/ea93a288dab77fe237975f084f586a9241ce53dd/build/media_source/vendor/tinymce/langs/fr.es5.js)

In French it is Conteneurs (plural)
See https://developer.mozilla.org/fr/docs/Web/CSS/Containing_block

I guess it should be translatable and therefore we would need a new string.

[Quiviro]

I have tested this item ✅ successfully on 05d476d

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[khu5h1]

I have tested this item ✅ successfully on 05d476d

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[Quy]

RTC

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[bembelimen]

Thx

[brianteeman]

Thanks