outdated docs: Directives

[keikoro]

Is it possible the documentation was never updated following PR #1482, in which the directives were reworked?

I don't know on which of the many branches of the repo the most current (live) docs live (develop? master? The traditional gh-pages branch also exists but looks dead), but this file here: https://github.com/mermaid-js/mermaid/blob/develop/docs/directives.md as well as the online documentation for Directives mention a separate config directive to modify e.g. font properties.

Confusingly, no-one seems to have noticed this or been bothered by it in a long time though folks have continued to open config-related issues (using a different syntax), so I'm not entirely sure I'm not confusing things here or looking in the wrong place.