Added js functions emulator.

Author: Reedyuk

firebase-common/src/jsMain/kotlin/dev/gitlive/firebase/externals.kt

@@ -92,6 +92,7 @@ external object firebase {
     object functions {
         class Functions {
             fun httpsCallable(name: String, options: Json?): HttpsCallable
+            fun useFunctionsEmulator(origin: String)
         }
         interface HttpsCallableResult {
             val data: Any?

firebase-functions/src/jsMain/kotlin/dev/gitlive/firebase/functions/functions.kt

@@ -26,7 +26,7 @@ actual class FirebaseFunctions internal constructor(val js: firebase.functions.F
     actual fun httpsCallable(name: String, timeout: Long?) =
         rethrow { HttpsCallableReference(js.httpsCallable(name, timeout?.let { json("timeout" to timeout.toDouble()) })) }
 
-    actual fun useFunctionsEmulator(origin: String): Unit = throw NotImplementedError()
+    actual fun useFunctionsEmulator(origin: String) = js.useFunctionsEmulator(origin)
 }
 
 @Suppress("UNCHECKED_CAST")