providers: Add quicksy.im
Quoted from joinjabber
Quicksy is a user-focused offer for Android by the developer of the Conversations App that allows you to easily create a Jabber account based on your mobile phone number. Other Quicksy users in your phone's contact list will be recognized by the app. Learn more about it on their website. You can register from within the Quicksy app:
The domain quicksy.im
is stated in the F-droid app description