[BUILD/RELEASE] Add pointers about creating the GitHub release

[shtrom]

This PR is a strawman, and not everything is functional, please don't merge without considering this.

Checklist

• [X] Feature

• [ ] Bug

• [ ] ChangeLog.md updated

• [ ] Tests added

• [ ] All testsuite passes

• [ ] make dist completed successfully

[shtrom]

No longer relevant. To be revisited within the Dockerised environment #62