docs: update readme with theme-aware logos

Author: benjamindotdev

README.md

@@ -1,4 +1,8 @@
-# stacksync
+<h1 align="center">
+  <img src="public/stacksync.svg#gh-light-mode-only" alt="StackSync" width="50" />
+  <img src="public/stacksync-white.svg#gh-dark-mode-only" alt="StackSync" width="50" />
+  StackSync
+</h1>
 
 ![License](https://img.shields.io/badge/license-MIT-blue.svg)