flask-redis: dev envs support & misc improvements (#265)

(Most of this is almost identical to #263.)

* Docker Desktop Development Environments config
* Use cache volumes for pip
* Downgrade from Python 3.11 _alpha_ -> Python 3.10
* Use port `8000` to avoid conflicts with Airplay on
    macOS for default Flask port `5000`
* Use `SIGINT` to gracefully stop Flask
* Formatting fixes in `compose.yaml`

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

flask-redis/.docker/docker-compose.yaml

@@ -0,0 +1,16 @@
+services:
+  redis:
+    image: redislabs/redismod
+    ports:
+      - '6379:6379'
+  web:
+    build:
+      context: .
+      target: dev-envs
+    stop_signal: SIGINT
+    ports:
+      - '8000:8000'
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    depends_on:
+      - redis