docs(gen): support language annotation in docstrings

runtime/lua/vim/treesitter.lua

@@ -313,7 +313,7 @@ end
 --- In this case, add ``vim.bo.syntax = 'on'`` after the call to `start`.
 ---
 --- Example:
---- <pre>
+--- <pre>lua
 --- vim.api.nvim_create_autocmd( 'FileType', { pattern = 'tex',
 ---     callback = function(args)
 ---         vim.treesitter.start(args.buf, 'latex')