Added Execution Indicator

src/main/java/net/fretux/knockedback/client/ClientExecutionState.java

@@ -0,0 +1,17 @@
+package net.fretux.knockedback.client;
+
+public class ClientExecutionState {
+    private static int timeLeft = 0;
+
+    public static void setTimeLeft(int ticks) {
+        timeLeft = ticks;
+    }
+
+    public static int getTimeLeft() {
+        return timeLeft;
+    }
+
+    public static boolean isExecuting() {
+        return timeLeft > 0;
+    }
+}