[Ratings & Reviews Prompt] Think about using this from a non-installed website

[jyasskin]

The basic functionality here, that navigator.requestReview() prompts to open a review site known to the browser with a query parameter identifying the caller, seems like it could be useful even for non-installed websites. Search engines, for example, could expose ratings for the sites they return.

There's a dependence on the manifest in https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/RatingsAndReviewsPrompt/explainer.md#the-handoff-to-a-catalog: that could stay, since non-installed sites can have manifests.

It'd be important to keep the UI quiet for non-installed sites, maybe along the lines of newer-style push-notification prompts.

#424 is a bit more exploitable in this case: consider passing just the origin to the review site?