Support compression on non-websocket responses

[scallopedllama]

Looks like initial support for compression is enabled for websockets but not for Responses on PageHandlers

[hoytech]

I implemented the compression for websockets. For my applications it has never seemed necessary to compress page handlers. First, because I rarely use them, and second because a reverse proxy such as nginx can compress HTTP responses effectively. AFAIK it can't or doesn't do it with websockets because this requires protocol level understanding of the stream.

That said, it's probably possible to adapt the compression code from websockets, I'd have to look at it more closely to say for sure. @mattgodbolt would know better than me of course.

[scallopedllama]

When I wrote up this feature request, I admit that I didn't really understand how compression over HTTP works. I recently did some work for #94 and understand it a bit better.
It could possibly be worked into the Connection::write method, calling into the ZLibContext to compress the data provided before transferring it out to the client.

I don't have as much use for this personally as most of the data I'll be sending back is pretty small (with the exception of files).