Add markdown parsing support

[Wilfred]

No description provided.

[Wilfred]

I can't find a mature, maintained implementation.

[jupblb]

Sorry to bump a closed issue but have you seen https://github.com/MDeiml/tree-sitter-markdown? It's already the default Markdown tree-sitter parser for https://github.com/nvim-treesitter/nvim-treesitter.

[gurjeet]

@Wilfred, I have created PR #380 to support Markdown. I haven't tested it extensively, but I believe we can add those tests later, as needed, to improve the coverage; or perhaps we can rely on the tests in the upstream project MDeim/tree-sitter-markdown, and not add any tests here.