docs: add more detail to WGs pages

[jcstein]

1. chair(s) of WG
2. short description of what each WG are here:
   1. https://cips.celestia.org/wgs/zk/index.html
   2. https://cips.celestia.org/wgs/da/index.html
   3. https://cips.celestia.org/wgs/interface/index.html
3. "standard" meeting schedule/cadence