What are Directives?
Directives are a way of controlling how Mermaid acts from within the diagram's code. The significance of this is that these options are available to you while you're writing the diagram. The configuration options from the directives are applied on top of the site-wide configurations that are set while you're integrating or setting up Mermaid on the website. There are some configuration options that you cannot change via directives by default for security reasons. You can modify the list of options that cannot be changed by directives while setting up Mermaid on the website.
The reason why directives exist is that there are some diagram features you should be able to change at an individual diagram level; these should not just be switched on or off globally on the website. This could be an aspect of a diagram such as whether to show a title, or whether to display actor names at the top and bottom of a sequence diagram. These aspects are better...
