Update README.md

Author: JakubSzark

README.md

@@ -88,6 +88,8 @@ If there are any issues with <b>complexity</b> please <b>open an issue</b>
 | deinit             | De-allocates the String                                                  |
 | find               | Finds first string literal appearance                                    |
 | rfind              | Finds last string literal appearance                                     |
+| includesLiteral    | Whether or not the provided literal is in the String                     |
+| includesString     | Whether or not the provided String is within the String                  |
 | init               | Creates a String with an Allocator                                       |
 | init_with_contents | Creates a String with specified contents                                 |
 | insert             | Inserts a character at an index                                          |