Improve community "blogs" (and more) feeds

[nul800sebastiaan]

Source: https://github.com/umbraco/OurUmbraco/blob/main/OurUmbraco.Site/config/CommunityBlogs.json

Currently this is part of the Our Umbraco codebase but it should be pulled out and put somewhere else (probably the upcoming community.umbraco.com website).

Thoughts for features:

• A web based form to submit your feed
• Moderation options in the backoffice once a new feed has been submitted
• Feed validation, a bit like the Umbraco Marketplace does
• Make a list of youtube and other feeds too (what other feeds can we think of?)