Prerender for crawlers feature request

Many static web apps (JS, Blazor WASM, etc.) require pre-rendering to be more SEO friendly.
Google crawler specifically handles JS apps quite well, but the crawler blocks DLL's so Blazor WASM isn't loaded properly.
Many other search engine crawlers don't execute the JavaScript at all.

There are ways to serve pre-rendered content when a crawler is detected, but this requires a backend or webserver supporting rewriting the request.
It would be a powerful selling point for Azure Static Web Apps to natively support pre-rendering of pages and serving them to crawlers.

The Chrome org has this project called [Rendertron](https://github.com/GoogleChrome/rendertron) which renders webpages including executing JavaScript (works with Blazor WASM) and returns a static rendered version (without JS). Integrating something like that or similar tech could add a lot of value IMO.

Alternatively, it would be great to extend the SWA routing system to allow rewriting the request for crawlers.