Setting `*.md.liquid linguist-language=Markdown` doesn't enable Markdown rendering with "Rich Diff" in GH pull request

[JLLeitschuh]

Describe the bug

Configuring *.md.liquid linguist-language=Markdown on a branch in .gitattributes should allow those files to be rendered on GitHub as markdown, supporting all features that markdown files have, including supporting rich diffing in pull requests.

Expected behaviour

I would expect setting *.md.liquid linguist-language=Markdown in .gitattributes would allow files with the *.md.liquid to support the rich diff view in pull requests.

Additional notes

Example pull request: ossf/omega-moderne-client#7

[lildude]

Linguist isn't responsible for the rendering of markup languages. That is controlled by the markup library which does not honour the Linguist overrides when it comes to rendering files which do not use one of these extensions.

This request has already been made twice in the markup repo: github/markup#1102 and github/markup#1069

Closing as this is not a Linguist issue.