Markdown: Select text and paste URL to create link

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What does this MR do and why?

Support pasting URLs in markdown

This behavior is relatively common in markdown-esque web editors, where, if you paste content that is a URL and have text already selected, the editor inserts the proper markup to make the selected text a link to the pasted URL.

References

See: #233393 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

QuickUrlPasteDemo_480

How to set up and validate locally

Here was my process to record the screen recording:

1. Connect to a GDK.
2. Check out the branch associated with this MR in the gitlab project in the GDK.
3. Enable the feature flag in bin/rails c

   Feature.enable(:markdown_paste_url, your_test_user)

4. Browse to that GDK's web interface, and open any issue.
5. Copy a URL to the clipboard, and select different regions of text, and paste the URL.