docs: update README.md [skip ci]

Author: allcontributors[bot]

README.md

@@ -1,4 +1,7 @@
 # express-asset-file-cache-middleware
+<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
+[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors-)
+<!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 ![Build Status](https://github.com/julianrubisch/express-asset-file-cache-middleware/workflows/Node%20CI/badge.svg)
 
@@ -115,3 +118,22 @@ $ npm test
 The MIT License (MIT)
 
 Copyright (c) 2019 Julian Rubisch
+
+## 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-start -->
+<!-- markdownlint-disable -->
+<table>
+  <tr>
+    <td align="center"><a href="http://www.julianrubisch.at"><img src="https://avatars0.githubusercontent.com/u/4352208?v=4" width="100px;" alt=""/><br /><sub><b>Julian Rubisch</b></sub></a><br /><a href="https://github.com/julianrubisch/express-asset-file-cache-middleware/commits?author=julianrubisch" title="Code">💻</a></td>
+  </tr>
+</table>
+
+<!-- markdownlint-enable -->
+<!-- prettier-ignore-end -->
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!