Document which extensions are bundled with Orbit

[zhumo]

1. It is not clear which extensions are bundled with Orbit. Should be documented
2. The additional tables that these extensions provide are not included in the query builder
3. When we take on the osquery docs into Fleet (Draft osquery schema for fleetdm.com and Fleet product #5045), we should include the additional tables in there as well
4. Tables that are added as part of bundled extensions should be marked as such.