[x] Update Sass README to mention the new Rouge assets, and explain how they work and which docs are/will be using it.
[x] Tweak Sass toolchain and all Highlight build scripts so that its docinfo files will be stored in _assets/hl/adoc/ instead of having a copy in every folder of the documents that rely on it.
[x] Update main README and add a table of which docs are using which highlighter, and maybe also mention their dependencies.
_assets/hl/adoc/instead of having a copy in every folder of the documents that rely on it.