fix: the local development failed to load the `src/assets/` images

[nusr]

Steps To Reproduce

• Run astro dev
• Markdown image path use /src/assets/

![something](@assets/images/example.jpg)
<!-- OR -->
![something](../../assets/images/example.jpg)

• Fail to load the image

https://docs.astro.build/en/guides/images/#configure-no-op-passthrough-service