[Feature request] Treesitter markdown groups

[carrascomj]

Related to #250, thanks to nvim-treesitter/nvim-treesitter@387a8f3

Description

Markdown tree-sitter is now available, providing different queries to match against and, most importantly, language injections for code blocks:

Feature request

I'd like to have this highlight when using onedark.vim and tree-sitter out of the box, since using tree-sitter deactivates the current onedark highlights on markdown (by default). For now, I have this in my tree-sitter config to achieve the above result:

require("nvim-treesitter.configs").setup({
	highlight = {
		enable = true,
		custom_captures = {
                        -- this should be Keyword but I prefer the hs in purple
			["text.title"] = "Question",
                       -- this does not work yet (problem with upstream I think)
			["text.reference"] = "Keyword",
			["text.emphasis"] = "markdownItalic",
			["text.uri"] = "markdownUrl",
		}
	},
})

Notice how the markdown tree-sitter does not provide the full spec yet.