Open https://josm.openstreetmap.de/wiki/Introduction page to the beginners

[openstreetmap.org-user-d1g]

(idea from #13214 could be extended to display Introduction)

Show an Introduction if user does something that tells he doesn't know JOSM workflow:

• click on a disabled mode (explained in #13214)
• click on a disabled menu item
• NO OSM DATA WAS LOADED after 30/60/90 seconds - this one is huge I think
• JOSM is closed shortly after (30-120 seconds) it was opened without single osm data layer was used during session
• click on a completely empty space in the interface (hard to implement in code I guess)

It should be reflected in the settings that user seen "Introduction" page; so that behavior affects only first-timers.

Maybe other users have better suggestions. My suggestions are way less distractive than iD/Potlatch behavior (display help at the first start without conditions).