compose: add ability to override image versions

Useful for local development, overriding to latest is possible now
without changing the compose file itself.

env.example

@@ -177,9 +177,6 @@ ETHERPAD_SKIN_VARIANTS="super-light-toolbar super-light-editor light-background
 # Wether to use starttls, implies LDAPv3 and requires ldap:// instead of ldaps://
 # LDAP_START_TLS=1
 
-# Container restart policy
-RESTART_POLICY=unless-stopped
-
 
 #
 # Security
@@ -206,3 +203,12 @@ JIBRI_RECORDER_PASSWORD=
 # XMPP password for Jibri client connections
 JIBRI_XMPP_PASSWORD=
 
+#
+# Docker Compose options
+#
+
+# Container restart policy
+#RESTART_POLICY=unless-stopped
+
+# Jitsi image version (useful for local development)
+#JITSI_IMAGE_VERSION=latest