Add licence.html to release quilkin.zip

[markmandel]

To make life easy if/when we add "notice" style dependencies, we need to include the licence with our distributions.

To solve this - do the work to include the licence.html file in our release .zip (which is easy enough to do) -- I'll write a ticket for this now so I remember to do it before the next release. The licence.html file is already in the Docker image.

Originally posted by @markmandel in https://github.com/googleforgames/quilkin/issues/856#issuecomment-1816889576