[Timeline] Add an option to HTML tool-tips to make them follow the cursor

[Feature request] From: #2498

It would be nice to have an option like tooltipFollowMouse, which when enabled will make the tool-tip follow the cursor.

It might be more beneficial to add a generic tooltip option, which accepts an object, and has followMouse as an acceptable sub-option. (As this then makes it cleaner if we want to add more options to tool-tips later)