Update Docker config

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.8-alpine
+FROM python:3.10-alpine
 
 RUN adduser -S fabcal
 

docker-compose.yml.example

@@ -7,7 +7,9 @@ services:
     ports:
       - 5000:5000
     environment:
-      - CALENDAR_URL=webcal://some.host/somecal
+      - FABCAL_CACHE_EXPIRE=120
+    volumes:
+      - ./config.yml:/app/config.yml
     # use the line below when running this behind reverse proxy (only if it sets the proxy headers, though)
     #command: --proxy-headers --forwarded-allow-ips="*"