Password Rules that are already defined using contraint validation attributes

To avoid duplication and future conflicts between a quirk and the website rules I'm not sure Password Rules should be accepted in the repo if the rules match what the page's markup already indicates via constraint validation attributes e.g. via `minlength`, `maxlength`, `pattern`, etc. The requirements for many sites can be expressed with those constraint validation attributes without the use of `passwordrules`.

Is that already covered by the `- [ ] The given rule isn't particularly standard and obvious for password managers` checklist item in the PR? If so, maybe that should be more clear and documented in CONTRIBUTING.md as well.