Parcel v2 Optimizer to replace process.envs

• reads .env file when NODE_ENV !== production, default process.cwd() + '.env' (full path can be overwritten by setting DOTENV_FILE - how ironic :D)
• replaces occurences of process.env.X with the value

How it works

• somehow hacky, because as an optimizer it just uses a dumb regex to replace all process.env with its values