Merge pull request #5072 from desktop/user-research-label

Add user research label

.github/CONTRIBUTING.md

@@ -159,6 +159,7 @@ pull requests.
 | `codemirror` | [search](https://github.com/desktop/desktop/labels/codemirror)  | Issues related to our use of [CodeMirror](https://codemirror.net/) that may require upstream fixes |
 | `electron` | [search](https://github.com/desktop/desktop/labels/electron) | Issues related to our use of [Electron](https://electron.atom.io) that may require upstream fixes |
 | `themes` | [search](https://github.com/desktop/desktop/labels/themes) | Issues related the light or dark themes that ship in Desktop |
+| `user-research` | [search](https://github.com/desktop/desktop/labels/user-research) | Issues that might benefit from user interviews, validations, and/or usability testing |
 
 #### Topics