Add @vitorarins as a contributor

Author: Igor Živković

.all-contributorsrc

@@ -0,0 +1,23 @@
+{
+  "projectName": "tinyproxy_exporter",
+  "projectOwner": "Igor Živković",
+  "repoType": "github",
+  "repoHost": "https://github.com",
+  "files": [
+    "README.md"
+  ],
+  "imageSize": 100,
+  "commit": true,
+  "contributors": [
+    {
+      "login": "vitorarins",
+      "name": "Vitor Arins",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/1065028?v=4",
+      "profile": "https://github.com/vitorarins",
+      "contributions": [
+        "bug",
+        "code"
+      ]
+    }
+  ]
+}

README.md

@@ -1,4 +1,5 @@
 # tinyproxy_exporter
+[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors)
 
 A simple Prometheus exporter for Tinyproxy.
 
@@ -17,3 +18,15 @@ optional arguments:
   -s STATHOST   internal statistics page address (default "tinyproxy.stats")
   -t TINYPROXY  tinyproxy address (default "127.0.0.1:8888")
 ```
+
+## Contributors
+
+Thanks goes to these wonderful people ([emoji key](https://github.com/kentcdodds/all-contributors#emoji-key)):
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore -->
+| [<img src="https://avatars3.githubusercontent.com/u/1065028?v=4" width="100px;"/><br /><sub><b>Vitor Arins</b></sub>](https://github.com/vitorarins)<br />[🐛](https://github.com/Igor Živković/tinyproxy_exporter/issues?q=author%3Avitorarins "Bug reports") [💻](https://github.com/Igor Živković/tinyproxy_exporter/commits?author=vitorarins "Code") |
+| :---: |
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+This project follows the [all-contributors](https://github.com/kentcdodds/all-contributors) specification. Contributions of any kind welcome!