Implement support for Gutenberg

[arnowelzel]

For Gutenberg it would be possible to create block which contains other blocks:

https://developer.wordpress.org/block-editor/how-to-guides/block-tutorial/nested-blocks-inner-blocks/

Based in this it may be possible to create a new block type for Gutenberg which can be displayed or hidden based on a Timed Content rule. However it is not clear yet, if a block can be hidden on the server side.