docs: add itsoum as a contributor for code (#538)

* docs: update CONTRIBUTING.md [skip ci]

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

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

.all-contributorsrc

@@ -122,7 +122,7 @@
       "name": "Peter Götz",
       "avatar_url": "https://avatars.githubusercontent.com/u/3618401?v=4",
       "profile": "https://github.com/petergtz",
-       "contributions": [
+      "contributions": [
         "code",
         "doc"
       ]
@@ -136,6 +136,15 @@
         "code",
         "doc"
       ]
+    },
+    {
+      "login": "itsoum",
+      "name": "Ilias Tsoumas",
+      "avatar_url": "https://avatars.githubusercontent.com/u/9675299?v=4",
+      "profile": "https://github.com/itsoum",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

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-12-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 -->
 
 ## Contributors ✨
@@ -29,6 +29,9 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="https://github.com/petergtz"><img src="https://avatars.githubusercontent.com/u/3618401?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Peter Götz</b></sub></a><br /><a href="https://github.com/py-why/dowhy/commits?author=petergtz" title="Code">💻</a> <a href="https://github.com/py-why/dowhy/commits?author=petergtz" title="Documentation">📖</a></td>
     <td align="center"><a href="https://github.com/bloebp"><img src="https://avatars.githubusercontent.com/u/51325689?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Patrick Blöbaum</b></sub></a><br /><a href="https://github.com/py-why/dowhy/commits?author=bloebp" title="Code">💻</a> <a href="https://github.com/py-why/dowhy/commits?author=bloebp" title="Documentation">📖</a></td>
   </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/itsoum"><img src="https://avatars.githubusercontent.com/u/9675299?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ilias Tsoumas</b></sub></a><br /><a href="https://github.com/py-why/dowhy/commits?author=itsoum" title="Code">💻</a></td>
+  </tr>
 </table>
 
 <!-- markdownlint-restore -->