Add a script element for opening books for players

[Moepius]

I suggest adding an element for the script editor, where the action opens a custom book for a player.

It would make it more user friendly to show links, also books are a better way to show texts and important information than chat, since it is static and no new messages flow in.

The player could provide the book as a custom item or a text file with custom text (some plugins do it this way).