Network.Framework and URLSession support for the Gemini Protocol

Calling URLProtocol.registerClass(GeminiProtocol.self) will cause your normal URLSession code to "Just Work" with gemini:// URLs. The URLResponse you receive will be a GeminiURLResponse with statusCode and meta properties.

• GeminiProtocol.swift contains the implementation of the URLSession support.
• GeminiNetwork.swift is a Network.framework implementation of a Gemini client.