docs: add mdboom as a contributor for maintenance (#615)

* 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

@@ -506,6 +506,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "mdboom",
+      "name": "Michael Droettboom",
+      "avatar_url": "https://avatars.githubusercontent.com/u/38294?v=4",
+      "profile": "http://droettboom.com",
+      "contributions": [
+        "maintenance"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -402,6 +402,7 @@ 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/justanotheranonymoususer"><img src="https://avatars.githubusercontent.com/u/5781692?v=4?s=100" width="100px;" alt="justanotheranonymoususer"/><br /><sub><b>justanotheranonymoususer</b></sub></a><br /><a href="https://github.com/EndBug/add-and-commit/issues?q=author%3Ajustanotheranonymoususer" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://cderv.rbind.io"><img src="https://avatars.githubusercontent.com/u/6791940?v=4?s=100" width="100px;" alt="Christophe Dervieux"/><br /><sub><b>Christophe Dervieux</b></sub></a><br /><a href="https://github.com/EndBug/add-and-commit/commits?author=cderv" title="Documentation">📖</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/deining"><img src="https://avatars.githubusercontent.com/u/18169566?v=4?s=100" width="100px;" alt="Andreas Deininger"/><br /><sub><b>Andreas Deininger</b></sub></a><br /><a href="https://github.com/EndBug/add-and-commit/commits?author=deining" title="Documentation">📖</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="http://droettboom.com"><img src="https://avatars.githubusercontent.com/u/38294?v=4?s=100" width="100px;" alt="Michael Droettboom"/><br /><sub><b>Michael Droettboom</b></sub></a><br /><a href="#maintenance-mdboom" title="Maintenance">🚧</a></td>
     </tr>
   </tbody>
 </table>