Add support for android SENDTO intent

[ChrisSmith2]

I use a popular running app called Strava. It has a feature to send a text before your run to one or more contacts, which you select in the app settings.
It seems BlueBubbles doesn't appear as an option in this dialog when trying to send the text:

I believe this is because BlueBubbles doesn't currently handle the intent android.intent.action.SENDTO.