Add a function to check what is the default browser

[Xayton]

In order to show the message about the "HTTPS Certificates" only to users that actually need it, we could check the default browser. If the user's default browser is Safari, we ask to install/update the certificates, otherwise we do nothing.

[Xayton]

Here the code that could be used by CGO:

const char *getDefaultBrowserName() {
    NSURL *defaultBrowserURL = [[NSWorkspace sharedWorkspace] URLForApplicationToOpenURL:[NSURL URLWithString:@"http://"]];
    if (defaultBrowserURL) {
        NSBundle *defaultBrowserBundle = [NSBundle bundleWithURL:defaultBrowserURL];
        NSString *defaultBrowser = [defaultBrowserBundle objectForInfoDictionaryKey:@"CFBundleDisplayName"];
        
        return [defaultBrowser cStringUsingEncoding:[NSString defaultCStringEncoding]];
    }

    return nil;
}

CC: @MatteoPologruto