Add pop-up tooltips when hovering over json file tokens to display add'l info

[Gazook89]

To provide additional info about a square set (imported json file), such as author, description, version, etc, a popup can be added when hovering over a json file token. It could also appear if clicking on the token (but not on the "remove token" button).

The popup should appear below the token in order to not obstruct the other tokens or the options menu.