Lack of keyboard accessibility

[RinkAttendant6]

It appears that the polyfill doesn't provide any keyboard accessibility to toggle the details element. I tried adding tabindex=0 to the <summary> element, which makes it focusable but not toggleable.

Both Chrome and Firefox allow the user to focus on the <summary> element and toggle the details using the Space or Enter keys.

It is probably not too difficult to implement, if I do get something working I will send over a pull request