Add examples to the types page

Hi! when working on the babel plugins, I really missed having examples of the types, something really simple such as

- [awaitExpression](https://astexplorer.net/#/gist/9952dc650522941e0229e6ea90c11a99/abea04c8a01690491c27df5e937b6dd43f2523f4) `await func()`

This makes it easy to find what syntax relates to particular expression types, as well as see them in the AST in context (through a link).

I ended up doing a lot of this for my own benefit over here: https://github.com/Noviny/babel-type-descriptions (most of those links are sadly now broken)

I wanted to know if finishing rounding out these types, and contrributing it to the types page on the website was something you would be interested in having?

Cheers!