add "Help Up" feature for knocked players, improve execution handling, and update mod version to 1.6.0

src/main/java/net/fretux/knockedback/HelpUpKnockedPacket.java

@@ -0,0 +1,36 @@
+package net.fretux.knockedback;
+
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraftforge.network.NetworkEvent;
+
+import java.util.function.Supplier;
+
+public class HelpUpKnockedPacket {
+    private final boolean helping;
+
+    public HelpUpKnockedPacket(boolean helping) {
+        this.helping = helping;
+    }
+
+    public static void encode(HelpUpKnockedPacket msg, FriendlyByteBuf buf) {
+        buf.writeBoolean(msg.helping);
+    }
+
+    public static HelpUpKnockedPacket decode(FriendlyByteBuf buf) {
+        return new HelpUpKnockedPacket(buf.readBoolean());
+    }
+
+    public static void handle(HelpUpKnockedPacket msg, Supplier<NetworkEvent.Context> ctx) {
+        ctx.get().enqueueWork(() -> {
+            ServerPlayer helper = ctx.get().getSender();
+            if (helper == null) return;
+            if (msg.helping) {
+                HelpUpHandler.startHelpUp(helper);
+            } else {
+                HelpUpHandler.cancelHelpUpByHelper(helper.getUUID());
+            }
+        });
+        ctx.get().setPacketHandled(true);
+    }
+}