Add toggle to hide review accuracy

[matchai]

Hey Tsurukame maintainers 👋

I'd love to see a simple toggle in the settings to hide the review accuracy % during reviews, much like the Hide Review Accuracy user script does.

It's a small change, but starting a review session with a few blunders drops the accuracy score and seeing my low accuracy discourages me. Installing the user script boosted my mood when reviewing – I'd love to see it added to the app. 😊