Add clarity that its constraints. (#54)

Author: Toys0125

content/docs/avatar/animation-rigging.mdx

@@ -1,10 +1,17 @@
 ---
-title: Animation Rigging
+title: Constraints
 ---
 import { Step, Steps } from 'fumadocs-ui/components/steps';
 import { Callout } from 'fumadocs-ui/components/callout';
 import { Accordion,Accordions } from 'fumadocs-ui/components/accordion';
 
+* Basis currently use Animation Rigging Package to provide constraints. 
+
+<Callout type="info">
+This package is used due to the lack of an open-source implementation of a multi-threaded constraint system. If anyone has the time or interest to develop one, contributions or new projects would be very welcome.
+</Callout>
+
+
 Documentation can be found for all the Constraints that Animation Rigging provides [here](https://docs.unity3d.com/Packages/com.unity.animation.rigging@1.4/manual/ConstraintComponents.html)
 
 ## Setup for Animation Rigging Packages