Add release process documentation

Description

This MR further documents how the project operates. Specifically, it

• Moves the documented changelog management process to the CONTRIBUTING doc.
• Adds a new RELEASE document that contains specific details on the release process
  • Details requirements for running release jobs
  • Documents the cadence of the scheduled release pipeline
  • Includes instructions on how to manually release a new version - important if the pipeline breaks and we need to deploy a fix
• Redirects from README.md to the detailed docs