expose job id as env var $STRIDER_JOB_ID

not sure if we should merge this... leaving it here to start the discussion of if strider-env's scope should be to expose Strider-specific vars too... it may be a good idea? maybe add check marks or something so that it's opt-in ? e.g. 

- [ ] Set STRIDER_JOB_ID ?

https://github.com/Strider-CD/strider/issues/496