added light and dark mode logos (#273)

* added light and dark mode logos

* switch dark and light logos

README.md

@@ -1,5 +1,9 @@
 <div align="center">
- <img alt="vision_agent" height="200px" src="https://github.com/landing-ai/vision-agent/blob/main/assets/logo.svg?raw=true">
+ <picture>
+  <source media="(prefers-color-scheme: dark)" srcset="https://github.com/landing-ai/vision-agent/blob/main/assets/logo_light.svg?raw=true">
+  <source media="(prefers-color-scheme: light)" srcset="https://github.com/landing-ai/vision-agent/blob/main/assets/logo_dark.svg?raw=true">
+  <img alt="VisionAgent" height="200px" src="https://github.com/landing-ai/vision-agent/blob/main/assets/logo_light.svg?raw=true">
+ </picture>
 
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