OverPlay - YouTube chat overlay in fullscreen

- Messages appear as semi-transparent bubbles of text.

- The message input area is invisible by default but shows up when you hover over the bottom area of the chat, or when you type something into it.

- The overlay is on the left side of the screen by default, but can be moved by dragging the drag handle on the top-left of the overlay, and can be resized by dragging the resize handle on the bottom right of the overlay.

This extension is currently rudimentary and there will likely be changes in the future.

This extension may sometimes break / cease functioning until fixed with an update, as YouTube's website code changes (and it may break for some people while still working fine for others due to YouTube's A/B testing).

Credits: the drag and resize handle icons were edited from icons obtained from UIcons by Flaticon (https://www.flaticon.com/uicons).