readSupportedPlatforms function
Read the platforms this plugin supports from the pubspec.yaml
Implementation
Set<String> readSupportedPlatforms(Map<String, dynamic>? flutter) {
if (flutter == null) return {};
final plugin = (flutter['plugin'] as Map?)?.cast<String, dynamic>();
if (plugin == null) return {};
final platforms = (plugin['platforms'] as Map?)?.cast<String, dynamic>();
if (platforms == null) return {};
return platforms.keys.toSet();
}