Initial structure and reference documents

Create initial repository structure and add the following
reference documents:

- charter: The authoritative copy of the TC charter (copied from wiki)
- members: Current TC members with election expiration
- programs.yaml: List of official programs including PTLs, codenames,
  mission statements...
- extra-atcs: List of people being granted an ATC exception

Change-Id: Ia2df3bf0808af8cfa306092442160d5ecb14dfb0