Remove transparent background for skip intro button

[bakkerthehacker]

This change allow more of the intro and credits to be viewed unobstructed while the skip button is present.

The skip button only takes up a small part of the video space, but the background stretches across the whole screen and isn't needed.

This single button without a background is also more inline with what the vanilla plex player does with its skip button.

[croneter]

Merged with e8a235d4523246ab1f207d944ab9d387032c14f1, many thanks!!