checkPlugin: Ensure that a peer dep for `ep_etherpad-lite` exists
checkPlugin: Ensure that a peer dep for `ep_etherpad-lite` exists

Tweak the new `updateDeps()` function and use it to add the
`ep_etherpad-lite` dependency if it is missing.

storytouch/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite