Auto-generate the release notes upon release

[thinkingserious]

Issue Summary

For every release, we hand craft the release notes on GitHub, now we would like to automate this process. Please see the existing release notes for an example. The contents of the release notes are generated from the CHANGELOG.md file. Here is the documentation for updating the release notes via the GitHub API.

Acceptance Criteria

• A script, which when run, creates a release note update based on the last deployed release

[duderman]

Can I take this one and the rest of them? (https://github.com/sendgrid/smtpapi-ruby/issues/80 & https://github.com/sendgrid/ruby-http-client/issues/96)

[childish-sambino]

Closing as we're now using internal tooling for this.