Wanikani Toggle Kanji Visibility

This script just adds buttons that can toggle the visibility of kanji and their readings when browsing through the kanji pages on Wanikani.
I wrote this script to be able to conveniently practice writing kanji that are taught on Wanikani.
You just open one of the kanji pages, look at the meanings, try to write the kanji, and then show them by clicking the toggle button to check if you were right!