Add file to releases page with SHA256 sums

[msabramo]

to give users an extra sense of security that they have a real, untampered-with download.

Example: See the consul_0.6.4_SHA256SUMS file at https://releases.hashicorp.com/consul/0.6.4/

Bonus points if you sign the file with a GPG key -- e.g.: consul_0.6.4_SHA256SUMS.sig

[kostyrev]

Will this ever be implemented?
I have no extra sense of security

[somethingwithproof]

I will get this into the CI/CD pipeline