Expose OSS binaries checksums in Download section

[remiguitreau]

When the eventstore binaries are downloaded directly from github (https://github.com/EventStore/EventStore/releases).
We cannot check the binaries signature in order to verify the integraty of the binary once downloaded.

An idea could be to deploy with the binaries a signature file (EventStore-OSS-v22.10.4-checksums.txt for example) which contains one line per binary with its signature (MD5, SHA256 ou SHA512)