Hope to add custom component documentation

[InfernalAzazel]

nicegui is very amazing, I have some suggestions:

1. I hope to separate the implementation of Vue css interaction into a python library
2. When developing web, most people will choose Vue3 react because there are too many components.（We should encourage the community to create components so that we have a variety of styles of components to choose from）

• I hope that in the future we can abandon Vue react and simply use python to develop web projects to achieve projects as exciting as Vue react.