feat: add lab7

Lab7/cs2030s/fp/Actionable.java

@@ -0,0 +1,17 @@
+package cs2030s.fp;
+
+/**
+ * Represent a container that can act on its content.
+ * CS2030S Lab 5
+ * AY22/23 Semester 1
+ *
+ * @param <T> The type of the content.
+ */
+interface Actionable<T> {
+  /**
+   * The method to act on its content.
+   *
+   * @param f The action.
+   */
+  void act(Action<? super T> f);
+}