add build-time validation for prefabs and other JSON assets

[keturn]

As requested by @skaldarnar.

https://github.com/diffplug/spotless/tree/main/plugin-gradle looks like a viable option.

[mmruii]

Hello, I want to work on this issue as my first project. I am a beginer and want to help solve this issue. Could you assign it to me?

[mmruii]

I went ahead and submitted a PR (#5326) with a proposed solution. I implemented a custom Gradle task ValidateJsonAssets that validates .prefab, .block, .ui and .json files at build time. Happy to receive feedback and make any adjustments. I also included unit tests