docs(examples): change react-router example to use UI Shell

.all-contributorsrc

@@ -1531,7 +1531,8 @@
       "avatar_url": "https://avatars.githubusercontent.com/u/7907338?v=4",
       "profile": "https://github.com/ychavoya",
       "contributions": [
-        "code"
+        "code",
+        "doc"
       ]
     },
     {

README.md

@@ -290,7 +290,7 @@ check out our [Contributing Guide](/.github/CONTRIBUTING.md) and our
     <td align="center"><a href="https://github.com/2nikhiltom"><img src="https://avatars.githubusercontent.com/2nikhiltom?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Nikhil Tomar</b></sub></a><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=2nikhiltom" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/aninaantony"><img src="https://avatars.githubusercontent.com/u/164350784?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Anina Antony</b></sub></a><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=aninaantony" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/ahmedsemih"><img src="https://avatars.githubusercontent.com/u/102798814?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ahmed Semih Erkan</b></sub></a><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=ahmedsemih" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/ychavoya"><img src="https://avatars.githubusercontent.com/u/7907338?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yael Chavoya</b></sub></a><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=ychavoya" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ychavoya"><img src="https://avatars.githubusercontent.com/u/7907338?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yael Chavoya</b></sub></a><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=ychavoya" title="Code">💻</a> <a href="https://github.com/carbon-design-system/carbon/commits?author=ychavoya" title="Documentation">📖</a></td>
     <td align="center"><img src="https://avatars.githubusercontent.com/u/37899503?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kilian Collender</b></sub><br /><a href="https://github.com/carbon-design-system/carbon/commits?author=Kilian-Collender" title="Code">💻</a></td>
   </tr>
   <tr>