setup y-indexeddb in client

[michaelpalumbo]

see 2nd code example here

verify:

• open a tab, move an op
• close all mischmasch tab(s)
• open mischmasch in a new tab
• observe that the op remained in new place

next add a simple widget in the index.html and main.js for storing/retrieving different scenes from y-indexeddb (create a new issue to track this progress)