isStyleUrlResolvable function
Whether url
resides within the current package or a dependency.
Implementation
bool isStyleUrlResolvable(String? url) {
if (url == null || url.isEmpty || url[0] == '/') return false;
var schemeMatch = _urlWithSchemaRe.firstMatch(url);
return schemeMatch == null ||
schemeMatch[1] == 'package' ||
schemeMatch[1] == 'asset';
}