fix FieldPath constructor in JS

Author: nbransby

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

@@ -182,7 +182,7 @@ external object firebase {
             fun clearPersistence(): Promise<Unit>
         }
 
-        open class FieldPath constructor(fieldNames: Array<out String>)
+        open class FieldPath constructor(vararg fieldNames: String)
 
         open class Query {
             fun get(options: Any? = definedExternally): Promise<QuerySnapshot>

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

@@ -342,8 +342,9 @@ actual class DocumentSnapshot(val js: firebase.firestore.DocumentSnapshot) {
 
 actual typealias FieldPath = Any
 
-actual fun FieldPath(vararg fieldNames: String): FieldPath = rethrow { firebase.firestore.FieldPath(fieldNames) }
-
+actual fun FieldPath(vararg fieldNames: String): FieldPath = rethrow {
+    js("Reflect").construct(firebase.firestore.asDynamic().FieldPath, fieldNames).unsafeCast<FieldPath>()
+}
 
 actual object FieldValue {
     actual fun delete(): Any = rethrow { firebase.firestore.FieldValue.delete() }