feat: time gutter position features

[bzbetty]

Allows the time gutter to be on the Left (default), Right, or Both

[cutterbl]

This looks really good. Only thing I see missing is a story under /stories/props.

[bzbetty]

Added in a story under /stories/props for TimeGutterPosition

[cutterbl]

OK, finally had a little more time to look at this. First, Thank You for your PR, and adding the base level documentation, though you did miss adding the prop/link to the Full Prop List.

A more detailed review shows one item that, while it doesn't appear to be currently causing an issue, may create one. The TimeGutter gets a ref. Currently you're assigning the same ref even when you have two gutters (left and right). This is used for measurement layout in the measureGutter() method. Might be nothing to worry about, but does set off some bells.