Update README.md

[Ged2323]

For some reason -> .installPlugin(.splash(withClassPrefix: "classPrefix"))
was not working and colouring the code properly though if you use -> ,plugins: [
.splash(withClassPrefix: "")
]
Splash colours work.

[uetcis]

I tried the latter one while it still doesn't work. It seems that the CSS file is neither referenced in the head of html pages nor copied to the generated folder.

[uhooi]

We can reference CSS from HTML by doing the following.
ref: uhooi/website-sample#3

extension Theme {
    static var uhooi: Self {
        Theme(
            htmlFactory: UhooiHTMLFactory(),
            resourcePaths: [
                "Resources/UhooiTheme/styles.css",
+               "Resources/SplashPublishPlugin/sundellsColors.css",
            ]
        )
    }
}

private struct UhooiHTMLFactory<Site: Website>: HTMLFactory {
    // ...
    func makeItemHTML(for item: Item<Site>,
                      context: PublishingContext<Site>) throws -> HTML {
        HTML(
            .lang(context.site.language),
-           .head(for: item, on: context.site),
+           .head(for: item, on: context.site, stylesheetPaths: [
+               "/styles.css",
+               "/sundellsColors.css",
+           ]),
        // ...
    }
    // ...
}