Add Boilr app: mobi.boilr.boilr

We would like to add Boilr to F-Droid. Boilr monitors cryptocurrencies and bullion prices, and triggers alarms according to user settings. It is licensed user GPLv3+.

With this merge request goes the necessary metadata. I tested both "fdroid build" and "fdroid checkupdates" and they run successfully.

For further info please refer to https://github.com/andrefbsantos/boilr and do not hesitate to contact me.