Only read body if it's Gemtext

I *think* this saves a bunch of bandwidth and speeds things up.

Remove pointless returns

Fix incorrect type in Sprintf call

Handle (somewhat) all possible Gemini response codes

Ignore new binary name

Add a basic, hacky, implementation

This also renames to gemlint (since just crawling isn't sufficient),
and removes cobra because we don't need the extra complexity right
now.

Add Gemini library

Centralise Copyright and licensing in the README

Import WTFNMFPL licensed skeleton