Docs: Add path tracer, ik library links to libraries and tools page (mrdoob#23876)

* Update Libraries-and-Plugins.html

* Update Libraries-and-Plugins.html

Author: gkjohnson

docs/manual/en/introduction/Libraries-and-Plugins.html

@@ -41,6 +41,12 @@ <h3>Intersection and Raycast Performance</h3>
 			<li>[link:https://github.com/gkjohnson/three-mesh-bvh three-mesh-bvh]</li>
 		</ul>
 
+		<h3>Path Tracing</h3>
+		
+		<ul>
+			<li>[link:https://github.com/gkjohnson/three-gpu-pathtracer three-gpu-pathtracer]</li>
+		</ul>
+		
 		<h3>File Formats</h3>
 
 		<p>
@@ -79,6 +85,7 @@ <h3>Inverse Kinematics</h3>
 		<ul>
 			<li>[link:https://github.com/jsantell/THREE.IK THREE.IK]</li>
 			<li>[link:https://github.com/lo-th/fullik fullik]</li>
+			<li>[link:https://github.com/gkjohnson/closed-chain-ik-js closed-chain-ik]</li>
 		</ul>
 
 		<h3>Game AI</h3>