feat(docker-compose): added a simple docker compose to get people started with example backend and frontend

package.json

@@ -17,6 +17,7 @@
     "lint:all": "lerna run lint --",
     "lint:type-deps": "node scripts/check-type-dependencies.js",
     "docker-build": "yarn bundle && docker build . -t spotify/backstage",
+    "docker-build:all": "yarn tsc && yarn build && yarn docker-build && yarn workspace example-backend build-image",
     "create-plugin": "backstage-cli create-plugin",
     "remove-plugin": "backstage-cli remove-plugin",
     "release": "if [ \"$(git symbolic-ref --short HEAD)\" = master ]; then echo \"don't try to release master\"; exit 1; else lerna version --no-push; fi",