Stanza polyfill for GHC2024

[alexfmpe]

On top of #1067

From https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/control.html :

Currently, GHC2021 is used by default if no other language edition is explicitly requested, for backwards compatibility purposes. Since later versions of GHC may use a different language edition by default, users are advised to declare a language edition explicitly. Using GHC2024 is recommended for new code.

These stanzas allow one to easily use GHC2021/GHC2024 while still building against 8.6/8.10

I have:

• Based work on latest develop branch
• Followed the contribution guide
• Looked for lint in my changes with hlint . (lint found code you did not write can be left alone)
• Run the test suite: $(nix-build -A selftest --no-out-link)
• Updated the changelog
• (Optional) Run CI tests locally: nix-build release.nix -A build.x86_64-linux --no-out-link (or x86_64-darwin on macOS)