Create maya-calendar.postinst

[lenemter]

Wait, can it be named not postinst?

[danirabbit]

@lenemter no because there are multiple packages created here, so we need to prefix with the package name so that debbuild knows which of these packages this postinst script belongs to

[lenemter]

@danirabbit Oh ok, just cheked in Debian manual and it should work.