Enable CI on postgres/postgres github repo?

Hi,

Now that the CI patch has been merged [1], perhaps it'd make sense to enable
that on the postgres/postgres mirror on github? See [2] for instructions.

Arguably it doesn't add that much, because cfbot runs builds using the
.cirrus.yml file all the time, but to me it still seems worthwhile: For one,
it actually does run windows builds sooner after a commit than the buildfarm
often does...

Greetings,

Andres Freund

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=93d97349461347d952e8cebdf62f5aa84b4bd20a
[2] https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob_plain;f=src/tools/ci/README