feat(package.json): add information urls to package

The changelog, documentation and license url has been added to the
package.json as these are used within the Unity package manager.

package.json

@@ -2,6 +2,9 @@
     "name": "io.extendreality.tilia.mutators.collisionignorer.unity",
     "displayName": "Tilia Mutators CollisionIgnorer Unity",
     "description": "Manages the collision states between a collection of GameObjects in the scene for the Unity software.",
+    "changelogUrl": "https://github.com/ExtendRealityLtd/Tilia.Mutators.CollisionIgnorer.Unity/blob/master/CHANGELOG.md",
+    "documentationUrl": "https://github.com/ExtendRealityLtd/Tilia.Mutators.CollisionIgnorer.Unity/tree/master/Documentation",
+    "licensesUrl": "https://github.com/ExtendRealityLtd/Tilia.Mutators.CollisionIgnorer.Unity/blob/master/LICENSE.md",
     "version": "1.2.15",
     "unity": "2018.3",
     "unityRelease": "10f1",