Add Docker Compose YAML File

Makes it easier to build & run the container with this command:

    $ docker-compose up -d --build

docker-compose.yml

@@ -0,0 +1,9 @@
+version: '3.7'
+
+services:
+  crontab-ui:
+    build: .
+    image: alseambusher/crontab-ui
+    network_mode: bridge
+    ports:
+      - 8000:8000