Update send-and-confirm-transaction.js

[kemargrant]

Return transaction signature.

[joncinque]

The change looks good, but just to get some background, how did you notice this issue? Looking at the code, I see that we thankfully never rely on the return from this function. Will it fix anything for your use case?

[kemargrant]

I actually use this file in my repo for soltalk. It was helpful for me if I can get the transaction signature from this function.
If anyone also decides to use it it will be nice that it is there.

[joncinque]

That's awesome -- cool project!