Add Typography support for RSS block

[benazeer-ben]

What?

Add typography support to the RSS block.
Part of #43242

Why?

RSS block is missing typography support.

How?

Adds the typography support via block.json

Testing Instructions

Go to the Global Styles setting ( under appearance > editor > styles > edit styles > blocks ).
Make sure that the RSS block's typography is configurable via Global Styles.
Verify that Global Styles are applied correctly in the editor and frontend.
Edit the template/page, Add RSS block and apply the typography settings.
Verify that block typography styles take precedence over global block settings.
Verify that block typography display correctly in both the editor and frontend.

Screenshots or screencast

Backend:

Frontend:

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: benazeer-ben <[email protected]>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @benazeer-ben! In case you missed it, we'd love to have you join us in our Slack community.

If you want to learn more about WordPress development in general, check out the Core Handbook full of helpful information.