Note on EnvPool Features

[cdmatters]

This is just a note to keep track of some useful EnvPool features:

• "Retries" - It would be good add an option to allow a certain number of retries if the Env crashes. It can be a little annoying if there is a single env that crashes and brings down training. Ideally, this could return a done, and restart, only truly crashing after say N failures.

• "Reset" - The envpool doesnt currently have a reset function! It probably should.