docs: add giedrius2020 as a contributor for code (#1295)

* 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

@@ -578,6 +578,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "giedrius2020",
+      "name": "Giedrius Juškevičius",
+      "avatar_url": "https://avatars.githubusercontent.com/u/71819123?v=4",
+      "profile": "https://github.com/giedrius2020",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -188,6 +188,7 @@ Thanks especially to the gracious help of Uproot contributors (including the [or
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/milesgranger"><img src="https://avatars.githubusercontent.com/u/13764397?v=4?s=100" width="100px;" alt="Miles"/><br /><sub><b>Miles</b></sub></a><br /><a href="https://github.com/scikit-hep/uproot5/commits?author=milesgranger" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/djw9497"><img src="https://avatars.githubusercontent.com/u/51672890?v=4?s=100" width="100px;" alt="djw9497"/><br /><sub><b>djw9497</b></sub></a><br /><a href="https://github.com/scikit-hep/uproot5/commits?author=djw9497" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/Pepesob"><img src="https://avatars.githubusercontent.com/u/113636251?v=4?s=100" width="100px;" alt="Piotr Sobczyński"/><br /><sub><b>Piotr Sobczyński</b></sub></a><br /><a href="https://github.com/scikit-hep/uproot5/commits?author=Pepesob" title="Code">💻</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/giedrius2020"><img src="https://avatars.githubusercontent.com/u/71819123?v=4?s=100" width="100px;" alt="Giedrius Juškevičius"/><br /><sub><b>Giedrius Juškevičius</b></sub></a><br /><a href="https://github.com/scikit-hep/uproot5/commits?author=giedrius2020" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>