Option for adding additional files

[ste101]

This patch works for me.
I think it could be done better.

Files can be added like this:

plugin.tx_http2 {
    settings {
        before {
            fontRegular.file = EXT:user_pizpalue/Resources/Public/Fonts/source-sans-pro-v14-latin-regular.woff2
            fontRegular.type = font
            fontRegular.mime = font/woff2
            fontRegular.crossorigin = anonymous
        }
        after {
            fontAwesome.file = EXT:user_pizpalue/Resources/Public/Fonts/fa-solid-900.woff2
            fontAwesome.type = font
            fontAwesome.mime = font/woff2
            fontAwesome.crossorigin = anonymous
            fontAwesome.rel = prefetch
        }
    }
}

With a little more other preload option could be added:
https://3perf.com/blog/link-rels/