Add Sneaking API for Entities

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java

@@ -870,6 +870,18 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         return Pose.values()[this.getHandle().getPose().ordinal()];
     }
 
+    // Paper start
+    @Override
+    public void setSneaking(boolean sneak) {
+        this.getHandle().setShiftKeyDown(sneak);
+    }
+
+    @Override
+    public boolean isSneaking() {
+        return this.getHandle().isShiftKeyDown();
+    }
+    // Paper end
+
     @Override
     public SpawnCategory getSpawnCategory() {
         return CraftSpawnCategory.toBukkit(this.getHandle().getType().getCategory());