Add a11y labels to the send button

[BasThomas]

Fixes #56

For reference:

Yeah, the only tricky thing is that at that point they would always be tied to the information passed into the function — if someone would want a different accessibilityLabel than the title, they would not be able to do so.

So we could add an optional parameter that would override the accessibilityLabel, just not sure if that's scalable enough / overkill.

[BasThomas]

What do you think @lenkaiser @rnystrom @gingerbeardman?

[gingerbeardman]

I think this is good, let's see what the future holds no point overthinking it at this point.