Add a screenshot and instruction for new users

[julgsk]

The feature

Hey guys,

Running SpamBlocker on GrapheneOS Android 16.
I struggled to enable SpamBlocker.

I faced the same problem as seen in these two issues 362 and 367.

Maybe just add in the README.md a mention to enable these two options? Options being a global activation and phone calls activation. Or maybe it's written black on white and I went too fast at some point during setup.
Screenshot included.

[aj3423]

That was my fault, the upgrading script in v4.11 should've handled this.

It doesn't seem clickable, now I've changed it to:

That would suffice.

Thanks for the suggestion.