Feature: Support CSS classes coming from WordPress block editor

[Zodiac1978]

Since WordPress 5.0 it has a new block editor. After several years this editor is now the standard editor and more and more people use those new blocks (buttons, columns, etc.) in posts.

But in the RSS feed, there is no CSS loaded from the website. So these layouts are broken.

For example, see these feeds:
https://syde.com/de/feed/
https://haurand.com/dewp-planet/

Classes like wp-block-button or wp-block-text-columns columns-2 could be a small optimization for WordPress blog feeds.

We don't need to offer the complete styles, but some basic styles for columns and buttons would be really neat.

Happy to help with finding and maintaining the correct class names from the WordPress project.

[Zodiac1978]

I will try to create a new theme with a working CSS addition to get a proof of my idea.

[Zodiac1978]

Thanks for the reaction @twlatl - can you maybe elaborate why you don't like this idea?

If this is out of scope for -which I can totally understand- what about adding a custom CSS option where the user could add their personal styling (or compatibility layer for their CMS, like in my case) without the need to create a complete theme?

[Zodiac1978]

Related issues #3657 #4398 #3341

A custom CSS option would make it possible that all these issues could be solved by the user and without creating a theme.