Allow validating YAML with inline yaml-language-server comments

[Destroy666x]

As title says, e.g.:

# yaml-language-server: $schema=https://raw.githubusercontent.com/compose-spec/compose-spec/master/schema/compose-spec.json

Pretty sure that's the most common way of describing schemas in YAML as of today. Would be nice to support it.

[sirosen]

I'm not familiar with this usage pattern, so I'll have to read up. This feels similar to #310.

It's likely that I'll first tackle #310 without including this, but I'll keep it in mind as a future use-case to make sure I leave room for it.

[vorburger]

I'm not familiar with this usage pattern, so I'll have to read up.

@sirosen FYI this is (possibly among others, I'm not 100% sure myself!) popular for folks (incl. me..) who use https://github.com/redhat-developer/vscode-yaml?tab=readme-ov-file#associating-a-schema-in-the-yaml-file. HTH!