Merge branch 'renovate/quay.io-hedgedoc-hedgedoc-1.x' into 'master'

Update quay.io/hedgedoc/hedgedoc Docker tag to v1.9.9

See merge request !59

webserver/docker_hackmd/templates/docker-compose.yml

@@ -3,7 +3,7 @@ version: "3"
 services:
 
   app:
-    image: quay.io/hedgedoc/hedgedoc:1.9.7-debian
+    image: quay.io/hedgedoc/hedgedoc:1.9.9-debian
     restart: always
     depends_on:
       - db