Return codespacePortForwardingDomain if we are running in codespaces.
Https://docs.github.com/en/codespaces/developing-in-codespaces/default-environment-variables-for-your-codespace#list-of-default-environment-variables.
Parameters
env: ProcessEnv = process.env
The environment variables from the environment of the current process.
Return codespacePortForwardingDomain if we are running in codespaces. Https://docs.github.com/en/codespaces/developing-in-codespaces/default-environment-variables-for-your-codespace#list-of-default-environment-variables.