Add transit plugin for ViaRail canadian long-distance trains railways

Canadian railways are a bit of a joke compared to Europe, but at least it seems there is standard open data available: https://www.viarail.ca/en/developer-resources

One day, we might even have high-frequency (and ideally high-speed) trains, so this might become a more interesting mode of transportation in the long run.

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Corresponding "Railway" app feature request: https://gitlab.com/schmiddi-on-mobile/railway/-/issues/86