magic-wormhole 0.18.0

Hello,

I am happy to announce that magic-wormhole 0.18.0 has been released.
A visible change is the default display of QR Codes, following the specification for file-transfer magic-wormhole codes.
This can be turned off with --no-qr

All changes in this release:

* Improve the example to act more like send/receive (#558, @OndrewBot)
* Display a QR code by default for "wormhole send" (#555, @ferada + @meejah)
  This encodes "wormhole-transfer:M-word0-word1" per the spec:
  https://github.com/magic-wormhole/magic-wormhole-protocols/blob/main/uri-scheme.md
* Add sequence diagram
* Support Read the Docs pull-request builds
* Drop support for Python 3.8 (#556)
* Add broken-link checker (#588, https://github.com/Cycloctane)
* Preemptively fix Click 8.2 (#584, @cjwatson)
* Basic support for PEP518 (#579, @SnoopJ)
* Add WORMHOLE_ACCEPT_FILE (#570, @haatveit)

thanks to all contributors and users,

meejah