Add compiled grammar to top level for use in linguist

[alexet]

Linguist needs a texmate grammar in a repository. The grammar is just a slightly modified version of the vscode one (the markdown grammar is different and doesn't have the same subrules). It seems easier to put it here where in future we can make it track the vscode grammar changes.

I plan to add a case to the action to fail if running the script changes the file but we want to get linguist support done soon.

[alexet]

I have accepted your suggestion.

[jcreedcmu]

Pity we can't expect people have jq, but the perl script is fine by me for now.

[jcreedcmu]

(with jq 1.6, one could do

jq 'walk(if type == "array" then map(select((type == "object" and has("include") and (.include | test("^text.html.markdown#" )) ) | not)) else . end)' /tmp/repo.json

to remove all objects with "include": "text.html.markdown#...")