(maint) Add documentation for environments api call

The environments resource was updated but documentation was not changed
to reflect the changes.

This commit adds the documentation to describe new functionality.
well, this is supposed to be a sample, and the text "Integer or 'unlimited'" is invalid. Suggest putting the value 180 there (the default 3 minutes expressed in seconds). To do more than that, add a line below the sample and state with words: "The environment_timeout attribute can also be the string "unlimited"".