Added Starkvind device control

[vangoft]

Added possibility to control Starkvind air purifiers with Dirigera hub.

air_purifier.py was tested with my own two purifiers to check functionality. class was written based on coding style in other classes.

test_air_purifier.py created and passing.

readme.md also updated.

i don't think any more tasks are open

[Leggin]

Thank you looks really good! CI is just complaining about trailing whitespace. If you have time to fix it great, if not I will merge it latest tomorrow and take care of it.

[vangoft]

All done! Hopefully the CI doesn't complain anymore :D

[Leggin]

awesome! thank you!