docs(gen): support language annotation in docstrings

runtime/lua/vim/lsp/diagnostic.lua

@@ -150,7 +150,7 @@ end
 ---
 --- See |vim.diagnostic.config()| for configuration options. Handler-specific
 --- configuration can be set using |vim.lsp.with()|:
---- <pre>
+--- <pre>lua
 --- vim.lsp.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(
 ---   vim.lsp.diagnostic.on_publish_diagnostics, {
 ---     -- Enable underline, use default values