Create initial template for foundations playbook.md

[anajsana]

This PR adds a new markdown called playbook.md which should include detailed documentation of the foundation's processes. (e.g. instructions on how to join a working group, file issues, or responsibilities of chairs).

The initial draft includes:

• Working Groups Guidelines
  • Principles
  • Roles
• Communication Channel Guidelines
• Linux Foundation's Policies

[anajsana]

Let's close without merging until the community feels ready to go through this