Improve markdown support.

[wzf03]

Improve markdown support use markdown_inline treesitter. It was tested to run well after nvim 0.9.0, and it should be run well in older version too.

[wzf03]

See https://github.com/nvim-treesitter/nvim-treesitter/issues/5397 , the latex parser cannot works properly in markdown file now. Using markdown_inline parser and parse the latex_block is a more stable way.

[wzf03]

https://github.com/nvim-treesitter/nvim-treesitter/pull/5857

There are another way to fix it by fixing the nvim-treesitter.

[wzf03]

nvim-treesitter/nvim-treesitter#5857

There are another way to fix it by fixing the nvim-treesitter.

Fixing in nvim-treesitter is better, and use markdown_inline may slow down the snippets.