[Bugfix] Disable http cache when cache is disabled

Long story short, we need to add a cache busting param to the end of the http request when cache is disabled to bypass http cache (even though most http calls come back as no-cache some of them apparently don't?)

Also added a section in the readme about the GW2 API not supporting CORS properly.

I'll eventually want to write up an adapter for using a capacitor plugin instead of axios, but that'll be for another time.