Introduce plusElement and minusElement to disambiguate situations like List<List<T>> + List<T>

#KT-9992 Fixed

js/js.libraries/src/core/kotlin_special.kt

@@ -488,6 +488,14 @@ public inline operator fun ShortArray.plus(elements: ShortArray): ShortArray {
     return this.asDynamic().concat(elements)
 }
 
+/**
+ * Returns an array containing all elements of the original array and then the given [element].
+ */
+@Suppress("NOTHING_TO_INLINE")
+public inline fun <T> Array<out T>.plusElement(element: T): Array<T> {
+    return this.asDynamic().concat(arrayOf(element))
+}
+
 /**
  * Sorts the array in-place.
  */