[ANNOUNCE] Wayland 1.21.0 release schedule

[Simon Ser]

Hi all,

Here is the release schedule for Wayland 1.21.0:

- Alpha: May 26th
- Beta: June 9th
- RC1: June 23rd
- First potential final release date: June 30th

Package maintainers are encouraged to pick up the pre-releases to make
sure packaging can be tested (and fixed) before the stable release.
This release will drop the autotools build system. Please make sure
you've migrated to Meson, feel free to open an issue if you run into a
bug.

Let me know if you'd like a pending patch to make it in the release.

Thanks,

Simon