Ability to manually (de)select items on the bulk add screen

[city41]

Discussed in https://github.com/city41/AMMiSTer/discussions/103

^{Originally posted by matijaerceg April 18, 2023} Right now, when you're adding games via bulk add, you can only add all the results. It would be nice if you could further deselect or select from the results to decide what to add.