Joplin (net.cozic.joplin)

See:

• rfp#434 (closed)
• https://github.com/laurent22/joplin/issues/15

I remove "react-native-camera" and "react-native-push-notification" because of Google GMS. Some features may not work (camera & alarms?).

The building is fine, but I can't install it on my device (I don't know why). Help is needed from here.
EDIT: I self-signed the APK, it now works!

I based my work on:

• https://gitlab.com/fdroid/fdroiddata/blob/master/metadata/com.mattermost.rnbeta.yml
• https://gitlab.com/fdroid/fdroiddata/blob/master/metadata/se.manyver.yml
• https://gitlab.com/fdroid/fdroiddata/blob/master/metadata/im.vector.alpha.yml

Ping: @laurent22 @licaon-kter @IzzySoft