Wagtail wish list: In resource page template, allow the "related page" to be an external link

[dorothyyeager]

Summary

What we are after:
In the resource page template, the "related page" block is used to generate the pages linked on the top right side as "read next."

Right now, we can only choose internal linked pages (so pages that are in Wagtail). There's no option to add an external link, which means we can't link in that spot to pages that are hard-coded (like data pages) , the transition page, or in some cases outside pages (like the IRS) that we might want to link.

Example of a "related page link" (the link in grey box, under red box labeled "read next")

Screenshot of what Wagtail user sees when generating that sidebar:

Related issues

#3445 Resource page image height wishlist item

Completion criteria

• Wagtail users can use either an internal link or external link to do related page links in the resource page template.

[johnnyporkchops]

@dorothyyeager, @kathycarothers. We don't have anything like ExternalLinkBlock currently, only ExternalButtonBlock, which renders as a button. I can make an ExternalLinkBlock though.
However, something else that I thought might be more versatile was a RichTextBlock option here, where you can always add a link to an external URL, but also put text in here as well, should the need ever arise.

Admin:

Rendering:

[dorothyyeager]

@johnnyporkchops I'm good with that solution! It accomplishes what we needed. Tagging @JonellaCulmer in case she has any style u/x concerns about it.

[JonellaCulmer]

@dorothyyeager @johnnyporkchops No issues, thanks for checking!

[kathycarothers]

@johnnyporkchops I am good too with that solution.