docs: add Shanduur as a contributor for code (#713)

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

.all-contributorsrc

@@ -121,6 +121,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "Shanduur",
+      "name": "Mateusz Urbanek",
+      "avatar_url": "https://avatars.githubusercontent.com/u/32583062?v=4",
+      "profile": "http://shanduur.github.io",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -9,7 +9,7 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/rancher/k3d?style=flat-square)](https://goreportcard.com/report/github.com/rancher/k3d)
 
 <!-- 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-13-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 [![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](code_of_conduct.md)
 
@@ -139,6 +139,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="http://wsl.dev"><img src="https://avatars2.githubusercontent.com/u/905874?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Nuno do Carmo</b></sub></a><br /><a href="#content-nunix" title="Content">🖋</a> <a href="#tutorial-nunix" title="Tutorials">✅</a> <a href="#question-nunix" title="Answering Questions">💬</a></td>
     <td align="center"><a href="https://github.com/erwinkersten"><img src="https://avatars0.githubusercontent.com/u/4391121?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Erwin Kersten</b></sub></a><br /><a href="https://github.com/rancher/k3d/commits?author=erwinkersten" title="Documentation">📖</a></td>
     <td align="center"><a href="http://www.alexsears.com"><img src="https://avatars.githubusercontent.com/u/3712883?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Alex Sears</b></sub></a><br /><a href="https://github.com/rancher/k3d/commits?author=searsaw" title="Documentation">📖</a></td>
+    <td align="center"><a href="http://shanduur.github.io"><img src="https://avatars.githubusercontent.com/u/32583062?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mateusz Urbanek</b></sub></a><br /><a href="https://github.com/rancher/k3d/commits?author=Shanduur" title="Code">💻</a></td>
   </tr>
 </table>