Devs can set theme using `.env` vars like production.
Devs can set theme using `.env` vars like production.

Allows developers to set the theme from the environment, which follows the pattern of production configuration.

[#176802099]

concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse