Editorial: Fix schema documentation for `flag` 
Editorial: Fix schema documentation for `flag` 

This was annoying to no end and had to make 2 dozen changes before figured out it was `flag` not `flags`.

  - [x] - Change documentation `flags` -> `flag`
  - [x] - Provide example for `flag`

  Addresses:
    - https://github.com/mdn/browser-compat-data/commit/a140245a75d23785d4a14deaa00790f08a6c0bb0

  References:
    - https://github.com/mdn/browser-compat-data/pull/623
teoli2003/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data