Add rewrite rule for Ghost cards

[jake-walker]

In Ghost articles, I find it difficult to read some of the links where the author makes use of link cards. After Miniflux's sanitisation the cards get reduced to a bit of a jumbled mess of image previews, favicons, links and descriptions (as shown below).

This PR adds a rewrite rule named fix_ghost_cards which extracts just the title and author from the card and converts it to a simple link.

Before

After

Guidelines

Do you follow the guidelines?

• I have tested my changes
• There are no breaking changes
• I really tested my changes and there is no regression
• Ideally, my commit messages follow the Conventional Commits specification
• I read this document: https://miniflux.app/faq.html#pull-request

[fguillot]

Is it possible to add a unit test?

[jake-walker]

Absolutely, I've added in a few unit tests to test the functionality and edge cases

[fguillot]

Would not be better to use a HTML list (<ul> / <li>) for readability when there are multiple cards? There is no spacing between each link which make it hard to read.

Example with this link: https://selfh.st/newsletter/2025-01-10/

Using fix_ghost_cards rewrite rule in Miniflux:

The original website:

[jake-walker]

I made a small change when adding the tests which messed up the formatting, but they definitely look better in a list. I've changed the code to do that and added a couple more tests: