docs: add kopfkrieg as a contributor (#301)

* docs: update README.md

* docs: create .all-contributorsrc

.all-contributorsrc

@@ -0,0 +1,24 @@
+{
+  "files": [
+    "README.md"
+  ],
+  "imageSize": 100,
+  "commit": false,
+  "contributors": [
+    {
+      "login": "kopfkrieg",
+      "name": "Florian",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/5047813?v=4",
+      "profile": "https://kopfkrieg.org",
+      "contributions": [
+        "review",
+        "doc"
+      ]
+    }
+  ],
+  "contributorsPerLine": 7,
+  "projectName": "watchtower",
+  "projectOwner": "containrrr",
+  "repoType": "github",
+  "repoHost": "https://github.com"
+}

README.md

@@ -1,4 +1,5 @@
 <p align="center">
+[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors)
   <img src="https://0x12b.com/watchtower-logo.png" width="450" />
 </p>
 <h1 align="center">
@@ -343,3 +344,15 @@ docker run -d \
   -e WATCHTOWER_NOTIFICATION_MSTEAMS_USE_LOG_DATA=true \
   containrrr/watchtower
 ```
+
+## Contributors
+
+Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore -->
+<table><tr><td align="center"><a href="https://kopfkrieg.org"><img src="https://avatars2.githubusercontent.com/u/5047813?v=4" width="100px;" alt="Florian"/><br /><sub><b>Florian</b></sub></a><br /><a href="#review-kopfkrieg" title="Reviewed Pull Requests">👀</a> <a href="https://github.com/containrrr/watchtower/commits?author=kopfkrieg" title="Documentation">📖</a></td></tr></table>
+
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!