* Handle duplicate atrules without children
We assumed that all At Rule nodes had children. Including ones that do not and should not — for example `@import url(…);`. Since this is not the case we’ll skip adding children for nodes that don’t have any.
* Update changelog
Co-authored-by: Jordi Marimon Palarea <jordimarimon7@gmail.com>
* move `./tests/jit` to `./tests`
* make tests consistent
Abstracted a `run` function and some syntax highlighting helpers for
`html`, `css` and `javascript`.