Avoid duplicates

[azumukupoe]

Describe the bug
avoid games being imported more than once

To Reproduce
Steps to reproduce the behavior:

1. use Import All
2. games already imported are imported again

Expected behavior
manager should avoid importing games more than once

Operating System

• Windows 10, 19042.685

Installed Launchers

• Epic Games Launcher
• Uplay
• ...

Screenshots
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Log
You can find the log file by opening the "Run" dialog by pressing Win+R, pasting %appdata%/steamgriddb-manager into it then pressing "OK". Upload it here as an attachment.

Additional context
Add any other context about the problem here.

[aranel616]

This is partially fixed in 6222596. Games that are imported will no longer appear in the list, and will no longer be imported more than once.

However, the game isn't removed from the list until you view the import tab a second time. If you click "Import" more than once without closing and reopening that tab, you can still get duplicate entries. Leaving this ticket open until that is also fixed.