docs: add bvolkmer as a contributor for code, and bug (#335)

* 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

@@ -131,6 +131,16 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "bvolkmer",
+      "name": "Benedikt Volkmer",
+      "avatar_url": "https://avatars.githubusercontent.com/u/7070761?v=4",
+      "profile": "https://github.com/bvolkmer",
+      "contributions": [
+        "code",
+        "bug"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -9,7 +9,7 @@
 [![PyPI version](https://badge.fury.io/py/httpx-oauth.svg)](https://badge.fury.io/py/httpx-oauth)
 
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-14-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-15-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <p align="center">
@@ -63,6 +63,9 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/lloesche"><img src="https://avatars.githubusercontent.com/u/2124094?v=4?s=100" width="100px;" alt="Lukas Lösche"/><br /><sub><b>Lukas Lösche</b></sub></a><br /><a href="https://github.com/frankie567/httpx-oauth/issues?q=author%3Alloesche" title="Bug reports">🐛</a> <a href="https://github.com/frankie567/httpx-oauth/commits?author=lloesche" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/king-jam"><img src="https://avatars.githubusercontent.com/u/8225465?v=4?s=100" width="100px;" alt="James King"/><br /><sub><b>James King</b></sub></a><br /><a href="https://github.com/frankie567/httpx-oauth/commits?author=king-jam" title="Code">💻</a></td>
     </tr>
+    <tr>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/bvolkmer"><img src="https://avatars.githubusercontent.com/u/7070761?v=4?s=100" width="100px;" alt="Benedikt Volkmer"/><br /><sub><b>Benedikt Volkmer</b></sub></a><br /><a href="https://github.com/frankie567/httpx-oauth/commits?author=bvolkmer" title="Code">💻</a> <a href="https://github.com/frankie567/httpx-oauth/issues?q=author%3Abvolkmer" title="Bug reports">🐛</a></td>
+    </tr>
   </tbody>
 </table>