docs: add joual as a contributor (testing-library#348)

* docs: update README.md

* docs: update .all-contributorsrc


Co-authored-by: null <allcontributors[bot]@users.noreply.github.com>

Author: allcontributors[bot]

.all-contributorsrc

@@ -736,6 +736,17 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "joual",
+      "name": "Joel Marcotte",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/157877?v=4",
+      "profile": "https://github.com/joual",
+      "contributions": [
+        "bug",
+        "test",
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,