add note on creating .env file
## Configure Environment Variables
In the root directory of the repo create a `.env` file. It is already listed in `.gitignore` so that anything you put in it would not accidentally leak into a public git repo. Refer to `.env.example` in the root of this repo for the mandatory and optional environment variables.
+From the root of the repository:
+
+```
+cp .env.example .env
+```
+
+In the newly created `.env` file, update the two values `CTR_REGISTRY` and `CTR_REGISTRY_PASSWORD` with appropriate values.
+
## Run the Demo
1. From the root of this repository execute `./demo/run-osm-demo.sh`.
