add several things to gradle properties

gradle.properties

@@ -1,5 +1,9 @@
 kotlin.code.style=official
 org.gradle.parallel=true
+kotlin.js.generate.externals=true
+kotlin.incremental=true
+kotlin.incremental.js=true
+
 kotlin_version=1.4.10
 kotlin_coroutines_version=1.3.9
 kotlin_serialisation_core_version=1.0.0-RC2