fix(docker): execute within /app

Author: bcanseco

Dockerfile

@@ -3,8 +3,8 @@ FROM node:14.3.0
 
 # When running as a GitHub Action, the WORKDIR is controlled by GitHub.
 # Furthermore, they recommend NOT setting it in the Dockerfile, which makes running locally difficult.
-# Thus we copy files to an /app directory to be used when running Docker outside GitHub Actions.
+# Thus we copy files to an /app directory to also be used when running Docker outside GitHub Actions.
 COPY . /app
 
 # Executing a shell is required for environment variable substitution when running as a GitHub Action.
-ENTRYPOINT ["sh", "-c", "npm install --production && npm start"]
+ENTRYPOINT ["sh", "-c", "cd /app && npm install --production && npm start"]