Make Vale's format support extensible

[jdkato]

See #688 (comment) for a related comment.

[XVilka]

One way to do that is to work with Tree-Sitter grammars the way NeoVim does—it will allow you to analyze comments in every language, depending on the syntax or so-called "injections".

[weaversam8]

+1 for tree-sitter- there are grammars for nearly every language and tree-sitter makes it easy to design your own.