docs(README): add sponsor

README.md

@@ -77,3 +77,9 @@ import { copy } from 'rcpy'; // "copy" is an alias of "rcpy"
 Authored and maintained by Sukka with help from contributors ([list](https://github.com/SukkaW/rcpy/graphs/contributors)).
 
 > [Personal Website](https://skk.moe) · [Blog](https://blog.skk.moe) · GitHub [@SukkaW](https://github.com/SukkaW) · Telegram Channel [@SukkaChannel](https://t.me/SukkaChannel) · Mastodon [@sukka@acg.mn](https://acg.mn/@sukka) · Twitter [@isukkaw](https://twitter.com/isukkaw) · Keybase [@sukka](https://keybase.io/sukka)
+
+<p align="center">
+  <a href="https://github.com/sponsors/SukkaW/">
+    <img src="https://sponsor.cdn.skk.moe/sponsors.svg"/>
+  </a>
+</p>