README: light and dark mode logo

Signed-off-by: Achille Roussel <[email protected]>

Author: achille-roussel

README.md

@@ -1,5 +1,8 @@
 <p align="center">
-<img src="https://github.com/dispatchrun/.github/blob/main/profile/dispatch_logo_light.png?raw=true" height="64"/>
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset=".github/blob/main/profile/dispatch_logo_dark.png?raw=true">
+    <img alt="dispatch logo" src=".github/blob/main/profile/dispatch_logo_light.png?raw=true" height="64">
+  </picture>
 </p>
 
 # dispatch-py