Bech32 typo detection

[fanquake]

It would be nice to have bech32 typo detection in the GUI.

sipa wrote a demo for this years ago:

http://bitcoin.sipa.be/bech32/demo/demo.html

Moved from bitcoin/bitcoin#16779

[Sjors]

We also have the RPC-side code for it now.

[meshcollider]

Please see #536