implement main functionality

src/main/java/ua/com/dxrkness/function/Action.java

@@ -0,0 +1,20 @@
+package ua.com.dxrkness.function;
+
+@FunctionalInterface
+public interface Action {
+    void execute();
+
+    default Action andThen(Action after) {
+        return () -> {
+            this.execute();
+            after.execute();
+        };
+    }
+
+    default Action compose(Action before) {
+        return () -> {
+            before.execute();
+            this.execute();
+        };
+    }
+}