resolve method
Try to resolve the source specification.
Returns a ResolvedSource if this provider can handle the
specification, or null to skip to the next provider.
Implementation
@override
Future<ResolvedSource?> resolve(SourceResolutionContext context) async {
final spec = context.specification;
if (spec is! LocalSource) return null;
final directory = spec.resolve(context.packageRoot);
if (directory == null) return null;
return ResolvedSource(directory: directory, origin: SourceOrigin.local);
}