Extension: Add HexFloatLiterals

[angerman]

Please include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.
• If the change is docs-only, [ci skip] is used to avoid triggering the build bots.

Please also shortly describe how you tested your change. Bonus points for added tests!

This is #4858 by @bgamari, with the changelog corrected.

[angerman]

/cc @bgamari

[23Skidoo]

Merged, thanks!