prefetch method
Implementation
void prefetch(String? url) {
if (url == null || url.isEmpty) return;
if (_strategy.get(url) != null) return;
_fetchAndCache(url);
}
void prefetch(String? url) {
if (url == null || url.isEmpty) return;
if (_strategy.get(url) != null) return;
_fetchAndCache(url);
}