Tiny change to the expandable-chapters plugin from https://github.com/DomainDrivenArchitecture/ to use smaller arrows.

Add it to your book.json configuration:

{
    plugins: ["expandable-chapters-small"]
}

Install your plugins using:

$ gitbook install

There is no configuration needed at the moment, can be left empty.

{
	"pluginsConfig": {
		"expandable-chapters-small":{}
	}
}