Update to reflect that React Router now supports scroll restoration

[danielnixon]

At the time I created this library, React Router (v5? v4?) had no support for scroll restoration. It does now (see https://reactrouter.com/en/6.6.2/start/overview#scroll-restoration).

• Does this conflict with what oaf-react-router does? Probably.
• Does it support focus restoration as well as scroll position? Probably not.
• Do we need to update this library? Probably.
• Do we need to update this readme? Definitely.

[danielnixon]

See remix-run/react-router#9555