Allow grouping of links about website-stalker

[EdJoPaTo]

I like the idea as often multiple Urls on the same site are tracked, I thought about it how to do it in a clean and neat way.
I dont have a perfect idea about it yet but I wanted to drop some thoughts here so I can find them again later.

#[serde(untagged)]
pub enum UrlVariants {
    Single(Url),
    Many(Vec<Url>),
}

pub struct Site {
  pub url: UrlVariants,
  #[serde(flatten)]
  pub options: Options,
}

pub struct Options {
  pub extension: String,
  …
  pub editors: Vec<Editors>,
}

which would result in something like you describe, just with the key url for both a single and multiple urls.

Downside on it: Site doesnt represent a single job to do anymore so maybe another, better idea might be to parse config entries into the Site objects to separate neat config from clean representation.

[EdJoPaTo]

added in 0921233