Update index.js

[tuutoo]

fix: fix a typo mobe -> move

[tuutoo]

BTW, in the same file, below code should also be updated.

The number should be < 10
If it happens to 9, the number will show as 9, but actually it should show as 09.

......
gridWidth.addEventListener("input", () => {
widthValue.innerHTML = gridWidth.value < 10 ? 0${gridWidth.value} : gridWidth.value;
});

gridHeight.addEventListener("input", () => {
heightValue.innerHTML = gridHeight.value < 10 ? 0${gridHeight.value} : gridHeight.value;
});
......