Create release template for a release checklist

[lumjjb]

Following up from https://github.com/guacsec/guac/pull/1733/files#diff-4a00447b47c36ebd3ded77321deff288e424f4605496ee1199fc9953a20f4473, it may be helpful to create a release template so that the maintainer doing the release can use a checklist.