docs: add Zethson as a contributor for code (#962)

* docs: update CONTRIBUTING.md [skip ci]

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

---------

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -272,6 +272,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "Zethson",
+      "name": "Lukas Heumos",
+      "avatar_url": "https://avatars.githubusercontent.com/u/21954664?v=4",
+      "profile": "https://lukasheumos.com",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,
@@ -280,5 +289,6 @@
   "repoType": "github",
   "repoHost": "https://github.com",
   "skipCi": true,
-  "commitConvention": "angular"
+  "commitConvention": "angular",
+  "commitType": "docs"
 }

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-29-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-30-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 ## Contributors ✨
@@ -50,6 +50,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     </tr>
     <tr>
       <td align="center" valign="top" width="14.28%"><a href="http://stjohngrimbly.com"><img src="https://avatars.githubusercontent.com/u/28342957?v=4?s=100" width="100px;" alt="St John Grimbly"/><br /><sub><b>St John Grimbly</b></sub></a><br /><a href="https://github.com/py-why/dowhy/commits?author=sgrimbly" title="Code">💻</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://lukasheumos.com"><img src="https://avatars.githubusercontent.com/u/21954664?v=4?s=100" width="100px;" alt="Lukas Heumos"/><br /><sub><b>Lukas Heumos</b></sub></a><br /><a href="https://github.com/py-why/dowhy/commits?author=Zethson" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>