add RESTRICT_GUEST_ACCESS to block unregistered users from all applications

.env.sample

@@ -18,6 +18,10 @@ SANDBOX_DOMAIN=sandbox.cryptpad.example.com
 #EXTRA_DOMAINS=', `www.cryptpad.example.com`'
 LETS_ENCRYPT_ENV=production
 
+## Set to true to block unregistered users from accessing any CryptPad applications
+## See https://docs.cryptpad.org/en/admin_guide/customization.html#restricting-guest-access
+#RESTRICT_GUEST_ACCESS=false
+
 ## SSO / OIDC (optional — uncomment below and add compose.sso.yml to COMPOSE_FILE to enable)
 # COMPOSE_FILE="$COMPOSE_FILE:compose.sso.yml"
 #SSO_ENABLED=true