text: Title: Add missing shell injection sinks
  Body: We should add missing `sinks` w.r.t. "shell injection" to  [`all_trigger_words.py`](https://github.com/python-security/pyt/blob/master/pyt/vulnerability_definitions/all_trigger_words.pyt). Refer to [Bandit plugin `shell_injection`](https://github.com/PyCQA/bandit/blob/master/bandit/plugins/injection_shell.py) for more info.