[Weather] Chore: Dark Sky can't generate new API Keys - change API

[DeeGeeTill]

The Issue
Forecast.io (Dark Sky) is no longer accepting new sign ups, so new users of the bot cog can no longer generate API keys. Dark Sky itself is going to stop at the end of 2021.

Possible Alternatives in Order of Suitability

• Open Weather Map
• AccuWeather
• Met Office (UK Government - so may be slightly inaccurate for international weather. Will still return a result with varying degrees of accuracy (great in major cities, good for ex-commonwealth, kind of 'eh' for everywhere else.)

EDIT: Spelling errors and incomplete sentence... oops...

[fixator10]

https://github.com/public-apis/public-apis#weather

[ltzmax]

wunderground seems also to be a choose to use as an api.