switch to use pnpm (#330)

Reviewed-on: https://gitea.com/gitea/docs/pulls/330
Co-authored-by: techknowlogick <techknowlogick@gitea.com>
Co-committed-by: techknowlogick <techknowlogick@gitea.com>

src/theme/MDXComponents/index.js

@@ -0,0 +1,7 @@
+import MDXComponents from '@theme-original/MDXComponents';
+import A from './A';
+
+export default {
+  ...MDXComponents,
+  a: A,
+};