docs: add kkothari2001 as a contributor for code, and test (#2964)

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

---------

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -401,6 +401,16 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "kkothari2001",
+      "name": "Kush Kothari",
+      "avatar_url": "https://avatars.githubusercontent.com/u/53650538?v=4",
+      "profile": "https://github.com/kkothari2001",
+      "contributions": [
+        "code",
+        "test"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -219,6 +219,7 @@ Thanks especially to the gracious help of Awkward Array contributors (including
     </tr>
     <tr>
       <td align="center" valign="top" width="14.28%"><a href="https://www.mloning.com/"><img src="https://avatars.githubusercontent.com/u/21020482?v=4?s=100" width="100px;" alt="Markus Löning"/><br /><sub><b>Markus Löning</b></sub></a><br /><a href="https://github.com/scikit-hep/awkward/commits?author=mloning" title="Documentation">📖</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/kkothari2001"><img src="https://avatars.githubusercontent.com/u/53650538?v=4?s=100" width="100px;" alt="Kush Kothari"/><br /><sub><b>Kush Kothari</b></sub></a><br /><a href="https://github.com/scikit-hep/awkward/commits?author=kkothari2001" title="Code">💻</a> <a href="https://github.com/scikit-hep/awkward/commits?author=kkothari2001" title="Tests">⚠️</a></td>
     </tr>
   </tbody>
 </table>