Theme responsive image assets

Inspired by [code.visualstudio.com](https://code.visualstudio.com/) homepage, make the docs image assets be theme responsive. This includes both static & animated assets.

![Image](https://github.com/user-attachments/assets/6569aea2-b51f-4e51-9d53-11a6dcb4946b)

![Image](https://github.com/user-attachments/assets/bda6e28f-f9f6-40f9-b2f5-d6d5d4170860)