Add usage example for virtual CCF container build and run

Signed-off-by: John Andersen <johnandersenpdx@gmail.com>

Author: pdxjohnny

Dockerfile

@@ -1,3 +1,8 @@
+# Usage
+#
+# Virtual CCF (non-SGX) build and run:
+#   $ docker build -t ghcr.io/scitt-community/scitt-api-emulator:main --progress plain .
+#   $ docker run --rm -ti -w /src/src/scitt-api-emulator -v $PWD:/src/src/scitt-api-emulator -p 8000:8000 ghcr.io/scitt-community/scitt-api-emulator:main
 FROM python:3.8
 
 WORKDIR /usr/src/scitt-api-emulater