Add passkey.isSupported method (#56)

Author: chrisfisher

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-native-authsignal",
-  "version": "1.5.0",
+  "version": "1.6.0",
   "description": "The official Authsignal React Native library.",
   "main": "lib/commonjs/index",
   "module": "lib/module/index",

src/passkey.ts

@@ -133,6 +133,19 @@ export class AuthsignalPasskey {
     }
   }
 
+  isSupported(): boolean {
+    if (Platform.OS === 'android') {
+      return Platform.Version >= 28;
+    } else if (Platform.OS === 'ios') {
+      return parseInt(Platform.Version, 10) >= 15;
+    } else {
+      return false;
+    }
+  }
+
+  /**
+   * @deprecated Use 'preferImmediatelyAvailableCredentials' to control what happens when a passkey isn't available.
+   */
   async isAvailableOnDevice(): Promise<boolean> {
     await this.ensureModuleIsInitialized();