Add SMHI as an weather provider for Sweden

[hnnweb]

Add SMHI (Swedish Meteorological and Hydrological Institute) as an weather provider for Sweden

[mendhak]

Thanks for that , looks good.

I'm just testing this and going to make a few changes. The weather symbol position in the JSON seems to change so I'll keep a part of the loop. And there's a comment about getting the min/max of the next XX hours, I'm just working on that now, I'll push it up. I've had to do this in another weather provider too so it isn't too difficult.

Some notes for myself:

• [x] Linting
• [ ] Testing
• [x] README
• [x] env.sh.sample
• [x] Changelog

[mendhak]

Thanks, done and merged. I've added to the changelog as well.