Promote this plugin to Fastify org

I think we can really increase the usage of this package by promoting it to a Core Plugin, it would definitely increase discoverability `@fastify/views` can stay to support third-party template engines, and this can be the "default and simpler" way to serve html (like how we both have `fastify-auth` and `fastify-basic-auth`) I also kinda want to decouple the [asset hasher](https://github.com/gurgunday/ghtml/tree/main/bin) from `ghtml` to remove all dependencies from it and maybe move it here? Since appending hashes to asset URIs is very tightly coupled to serving html WDYT? I think the team would be down since it's a very simple plugin