[Documentation]: Introduction and Application Specific Section Update

[samricotta]

Summary

This section can be updated https://docs.cosmos.network/main/learn/intro/why-app-specific. It's a bit dated and doesn't really give any analogies so people can relate. People are quite confused what Sovereign Application Specific blockchains are.

https://celestia.org/learn/beginners/the-modular-stack/ this is a good example of an analogy to help people understand.

In conferences I've used a lego analogy before. This could also reference to modularity etc