[DOC] Made light/dark mode for Chroma logo (#5215)

Before: <img width="899" height="454" alt="Screenshot 2025-08-06 at 11 43 36 AM" src="https://github.com/user-attachments/assets/22b1463e-34b3-4031-a8fe-c066aa2c2c59" /> After: <img width="1032" height="454" alt="Screenshot 2025-08-06 at 11 44 10 AM" src="https://github.com/user-attachments/assets/28ddc65f-9655-4163-8f6a-5127c923061c" /> <img width="1032" height="454" alt="Screenshot 2025-08-06 at 11 44 32 AM" src="https://github.com/user-attachments/assets/9e1ff604-760e-4075-9383-04ae8204c7c3" />

Author: kylediaz

README.md

@@ -1,5 +1,8 @@
 <p align="center">
- <a href="https://trychroma.com"><img src="https://user-images.githubusercontent.com/891664/227103090-6624bf7d-9524-4e05-9d2c-c28d5d451481.png" alt="Chroma logo"></a>
+ <picture>
+  <source media="(prefers-color-scheme: dark)" srcset="https://github.com/user-attachments/assets/114a5e42-b0fb-40b1-8eaf-3314d61481c7">
+  <img alt="Chroma Logo." src="https://github.com/user-attachments/assets/8bb398b7-b98d-42fe-9c37-9982d1a5d6b2">
+ </picture>
 </p>
 
 <p align="center">