feat: add up -e/--env support

[starpit]

Is your feature request related to a problem? Please describe.
-e foo=bar would be sugaring over --set foo=bar and an app.yaml that sets the corresponding env var based on helm templates, e.g.

env:
  - name: foo
     value: {{ .Values.foo }}

The advantage being the application owner doesn't need to be the conduit for env vars into the app. Instead, lunchpail can do this for them.