Add MeshShape docs;

api/lovr/physics/MeshShape/init.lua

@@ -0,0 +1,8 @@
+return {
+  summary = 'A mesh Shape.',
+  description = 'A type of `Shape` that can be used for triangle meshes.',
+  extends = 'Shape',
+  constructors = {
+    'World:newMeshCollider'
+  }
+}

api/lovr/physics/Shape/init.lua

@@ -11,6 +11,7 @@ return {
     'World:newBoxCollider',
     'World:newCapsuleCollider',
     'World:newCylinderCollider',
-    'World:newSphereCollider'
+    'World:newSphereCollider',
+    'World:newMeshCollider'
   }
 }