add Import/Export for Nicknames

[T0biii]

Hey we wanted to exchange nicknames among friends, so we came up with the idea of ​​adding import and export buttons to the Nicknames view.
This is my first time with C++ code, so feedback is very welcome.

Tested on Ubuntu:

[github-actions]

clang-tidy made some suggestions

[pajlada]

I don't mind this feature, but if the goal is to share nicknames between friends I'd prefer if this used something like your system clipboard instead.

So the export button would export the nickname json to your clipboard, and the import button would read that json blob from your clipboard

The label of the buttons should probably be updated to reflect that change as well. "Import from clipboard" and "Export to clipboard" if it fits.
If it doesn't fit where they are now, you can move it to below the nicknames instead.

[T0biii]

I think it's easier to share a file depending on how many nicknames are present, e.g. Discord has a character limit of 2000. 4000 for Nitro Users.
But if you think clipboard would be better i can try to update the pr to clipboard

as example:
the 4 Nicknames in the example above already 445 charcaters

[pajlada]

I did not consider character limits, let me give it a think

[github-actions]

clang-tidy made some suggestions

[pajlada]

Sorry for the delay!

I think files are fine, however I think I'd like to be a bit forward-thinking with the import & export format.
Currently you're exporting the nicknames as-is. I'd prefer if we provide some metadata alongside the export that can be used in the import.

I think something like this would be good:

{
    "type": "nickname_export",
    "version": "1",
    "comment": "Exported from Version::instance().buildString() at CURRENT TIME",
    "data": [
        // the nicknames in the same format you were already using
    ]
}

I'm not convinced of the place for the "exportNicknames" and "importNicknames" functions, so I might want to move those around a bit but that's easy to do as a last step.