fixed missed command registration for extension, 1.3.0, added optional version.

gradle.properties

@@ -9,7 +9,7 @@ org.gradle.jvmargs=-Xmx1G
 	loader_version=0.7.2+build.174
 
 # Mod Properties
-	mod_version = 1.2.6+v191209
+	mod_version = 1.3.0+v191210
 	maven_group = carpet
 	archives_base_name = fabric-carpet