fix(ts): escape lang when loading parsers (#16668)

When trying to load a language parser, escape the value of
the language.

With language injection, the language might be picked up from the
buffer. If this value is erroneous it can cause `nvim_get_runtime_file`
to hard error.

E.g., the markdown expression `~~~{` will extract '{' as a language and
then try to get the parser using `parser/{*` as the pattern.

runtime/lua/vim/treesitter/language.lua

@@ -14,7 +14,7 @@ function M.require_language(lang, path, silent)
     return true
   end
   if path == nil then
-    local fname = 'parser/' .. lang .. '.*'
+    local fname = 'parser/' .. vim.fn.fnameescape(lang) .. '.*'
     local paths = a.nvim_get_runtime_file(fname, false)
     if #paths == 0 then
       if silent then