Support path for client cert usage

[makew0rld]

So in the config, you could specify:

"example.com/dir/" = "/path/to/cert.pem"

And then the cert would only be sent when visiting /dir/ or anything below.

[makew0rld]

This issue should mean that full URLs are supported in that section, as well as just hosts. So specifying things like gemini://example.com and //example.com/, etc, should all work once this is closed. Query strings and fragments should be parsed and ignored.