chore: improve documentation for the Dialog API

[novitpw]

This PR improves the documentation for the dialog API example, as several issues were noticed after reading it. The PR includes the following fixes:

• Using UUID instead of PlayerCommonConnection
• Using ConcurrentHashMap, since events are triggered in different threads
• One-minute timeout to prevent the player connection from hanging indefinitely
• Manually closing the dialog using Audience#closeDialog, as the client sometimes doesn't do this if no button was pressed (e.g., in case of a timeout)
• All of this includes a bit of adherence to best practices ;)

[github-actions]

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[olijeffers0n]

Nice

[MrPowerGamerBR]

The only nitpack that I have is that it would be nice to show how you can also clean up the map using the PlayerConnectionCloseEvent event too.

[Strokkur424]

Thank you for the pull request!