chore: add sponsor buttons

.github/FUNDING.yml

@@ -0,0 +1,4 @@
+github: johackim
+ko_fi: johackim
+liberapay: johackim
+custom: ['https://www.buymeacoffee.com/johackim', 'https://donate.stripe.com/4gw2bn85z5k57uw4gh']

README.md

@@ -42,6 +42,20 @@ Options:
 make test
 ```
 
+## Support me
+
+I'd love to work on this project, but my time on this earth is limited, support my work to give me more time!
+
+Please support me with a one-time or a monthly donation and help me continue my activities.
+
+[![Github sponsor](https://img.shields.io/badge/github-Support%20my%20work-lightgrey?style=social&logo=github)](https://github.com/sponsors/johackim/)
+[![ko-fi](https://img.shields.io/badge/ko--fi-Support%20my%20work-lightgrey?style=social&logo=ko-fi)](https://ko-fi.com/johackim)
+[![Buy me a coffee](https://img.shields.io/badge/Buy%20me%20a%20coffee-Support%20my%20work-lightgrey?style=social&logo=buy%20me%20a%20coffee&logoColor=%23FFDD00)](https://www.buymeacoffee.com/johackim)
+[![liberapay](https://img.shields.io/badge/liberapay-Support%20my%20work-lightgrey?style=social&logo=liberapay&logoColor=%23F6C915)](https://liberapay.com/johackim/donate)
+[![Github](https://img.shields.io/github/followers/johackim?label=Follow%20me&style=social)](https://github.com/johackim)
+[![Mastodon](https://img.shields.io/mastodon/follow/1631?domain=https%3A%2F%2Fmastodon.ethibox.fr&style=social)](https://mastodon.ethibox.fr/@johackim)
+[![Twitter](https://img.shields.io/twitter/follow/_johackim?style=social)](https://twitter.com/_johackim)
+
 ## License
 
 This project is licensed under the GNU GPL v3.0 - see the [LICENSE.txt](LICENSE.txt) file for details