Document Array and String get() function behavior (KT-30141)

libraries/stdlib/unsigned/src/kotlin/UShortArray.kt

@@ -17,10 +17,20 @@ internal constructor(@PublishedApi internal val storage: ShortArray) : Collectio
     /** Creates a new array of the specified [size], with all elements initialized to zero. */
     public constructor(size: Int) : this(ShortArray(size))
 
-    /** Returns the array element at the given [index]. This method can be called using the index operator. */
+    /**
+     * Returns the array element at the given [index]. This method can be called using the index operator.
+     *
+     * If the [index] is out of bounds of this array, throws an [IndexOutOfBoundsException] except in Kotlin/JS
+     * where the behavior is unspecified.
+     */
     public operator fun get(index: Int): UShort = storage[index].toUShort()
 
-    /** Sets the element at the given [index] to the given [value]. This method can be called using the index operator. */
+    /**
+     * Sets the element at the given [index] to the given [value]. This method can be called using the index operator.
+     *
+     * If the [index] is out of bounds of this array, throws an [IndexOutOfBoundsException] except in Kotlin/JS
+     * where the behavior is unspecified.
+     */
     public operator fun set(index: Int, value: UShort) {
         storage[index] = value.toShort()
     }