Update timer.ytag (#176)

Update timer tag to use events, as the mixin is quite overkill now

Author: cputnam-a11y

tags/guide/timer.ytag

@@ -8,35 +8,28 @@ DO NOT use threads or `java.util.Timer`. (This can cause a crash!) Instead:
 
 - If you are making a block do something in the future: `world.scheduleBlockTick` + override `scheduledTick` in your `Block`.
 - If you are making a custom tickable stuff (usually block entity/entity) do something in the future/periodically: see below, but instead of Mixin just implement yourself
-- If you are making a vanilla tickable thing (world, server, etc) do something in the future/periodically: use the following mixin.
+- If you are making a vanilla tickable thing (world, server, etc) do something in the future/periodically: use the relevant tick event similar to the following.
 
 ```java
-@Mixin(StuffToTick.class) // ServerWorld, MinecraftServer, etc
-public class StuffTimer implements StuffTimerAccess {
-    @Unique
-    private long ticksUntilSomething;
-
-    @Inject(method = "tick", at = @At("TAIL"))
-    private void onTick(CallbackInfo ci) { // Fix parameters as needed
-        if (--this.ticksUntilSomething == 0L) {
-            doSomething();
-            // If you want to repeat this, reset ticksUntilSomething here.
+    public static class StuffTimer implements ServerTickEvents.EndTick {
+        public static final StuffTimer INSTANCE = new StuffTimer();
+        private long ticksUntilSomething;
+        public void setTimer(long ticksUntilSomething) {
+            this.ticksUntilSomething = ticksUntilSomething;
+        }
+        @Override
+        public void onEndTick(MinecraftServer server) {
+            if (--this.ticksUntilSomething == 0L) {
+                doSomething();
+                // If you want to repeat this, reset ticksUntilSomething here.
+            }
+        }
+        public static void register() {
+            ServerTickEvents.END_SERVER_TICK.register(INSTANCE);
         }
     }
-
-    @Override
-    public void yourmod_setTimer(long ticksUntilSomething) {
-        this.ticksUntilSomething = ticksUntilSomething;
-    }
-}
-```
-```java
-public interface StuffTimerAccess {
-    void yourmod_setTimer(long ticksUntilSomething);
-}
 ```
 Usage:
 ```java
-MinecraftServer server;
-((StuffTimerAccess) server).yourmod_setTimer(100L); // do something after 100 ticks
+    StuffTimer.INSTANCE.setTimer(100L); // do something after 100 ticks
 ```