Request intercept and proxy improvements

I've been pushing the limits of this library a lot and ran into a few limitations that I was working around. I'm now coming back and

Added support for a lot more mime/content types. Maintained the same fallback values as before.
Improved support for MainFile such that it can be a URL with query string parameters. Allows the main file to point to the proxy.
Added support for custom response headers via the proxy.
Cleaned up some repetitive code to ensure more consistency between platforms.
Extended proxy sample to demonstrate how it can be used to access resources on non-CORs enabled endpoints.
Added an example wraps the HybridWebView in a class library to create a custom control. It uses the proxy to load the main page and an image as embedded resource. Added a page to the main sample that loads this custom control.
Improve stability of query string parsing
Add example that leverages the improvements to MainFile loading and a proxy to load web pages and resources from the file system (app data directory).

Eilon / MauiHybridWebView