Added "Feels-like" temperature

[sungkhum]

• [x] This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• [x] I have thoroughly tested my contribution.
• [x] Should this code require changes to documentation I will contribute those to https://github.com/ThingPulse/docs.

/<Description of and rationale behind this PR> Calculations credit goes to https://gist.github.com/jfcarr/e68593c92c878257550d I don't know C++ so I don't know if I added the code in the best place. It does work for me (I'm able to display the value with currentWeather.feelsLikeTemp). I hope others find this number useful.

I also added code so it works in metric and imperial (thanks @G6EJD for the reminder).

[akrinke]

It seems OpenWeatherMap added a new "feels_like" temperature value to the current weather data; see https://openweathermap.org/current#current_JSON and the blog post at https://openweather.co.uk/blog/post/new-feels-temperature-openweather-apis

[marcelstoer]

Yep, I also noticed, thanks. So this can now be simplified to just map the new property.

[marcelstoer]

e1e3674 replaces this -> closing