Add support for label and field selectors in informers

- Add InformOptions struct with ListOptions and ResyncPeriod fields
- Update all client methods to accept options parameters
- Add comprehensive examples in main.go demonstrating:
  - Label selector filtering (test=example)
  - Field selector filtering (status.phase=Running)
  - Custom resync periods
- Add tests for label and field selectors with mock query parameter support
- Fix nil pointer handling in all client methods
- Update mock transport to handle query parameters correctly

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -33,7 +33,7 @@ if err != nil {
     log.Fatal(err)
 }
 
-err = cmClient.Create(ctx, "default", &corev1.ConfigMap{
+cm, err = cmClient.Create(ctx, "default", &corev1.ConfigMap{
     ObjectMeta: metav1.ObjectMeta{
         Name: "my-config",
     },