[Research] Easier way to add custom classes

[nathan-schmidt-viget]

There is not an easy to add a custom class to the child element(s) of a custom block or a core WP block. This would be really nice to have to add in TW classes.
It can't be added in the WP editor "class" section as that can easily be removed.

Look into:

• WP filters
• WP React
• WP theme.json