Add Entity.has to check if entity has a value

src/entity.zig

@@ -254,6 +254,14 @@ pub fn Entity(comptime ctx: anytype) type {
             return if (result != 0) fromRaw(self.world, result) else null;
         }
 
+        /// Returns whether this `Entity` has the specified value.
+        ///
+        /// `value` must be convertible to an id. See also: `util.anyToId(...)`.
+        pub fn has(self: Self, value: anytype) bool {
+            const id = util.anyToId(ctx, value);
+            return c.ecs_has_id(self.world.raw, self.raw, id);
+        }
+
         pub fn get(self: Self, comptime T: type) ?*const T {
             const id = Lookup(ctx, T).id;
             return @alignCast(@ptrCast(c.ecs_get_id(self.world.raw, self.raw, id)));