[Ratings & Reviews Prompt] Encourage UAs to give the option of never prompting

I'd encourage this spec to have a "should" level requirement that UAs allow a configuration mode that never prompts for reviews (i.e. always returns disallowed, with no user interruption).

To some folks, these review prompts are quite annoying and interrupting. Personally, whenever I get one, I take the time to go leave a one-star review saying "This stupid app interrupted my attempts to use it to get me to leave this review. So, automatic one-star." Judging by my sibling one-star reviews, I'm not the only one who does this.

On the web platform, we generally take a stronger stand against abuse and user annoyance than many native platforms. So I hope implementations of this API allow turning off such prompting. IMO the ideal place for this would be a checkbox below the currently-depicted "Don't ask again for this app", which instead says something like "Don't ask again for any apps installed by Microsoft Edge". (But that is, of course, a per-browser UI decision.)

Otherwise, I think the introduction of this API will likely depress PWA installation for at least some users, since avoiding installation seems like it will be the only way to stay safe from these prompts in the current design.