Add typescript definition file (#376)

* Add typescript definition file

* Update index.d.ts

index.d.ts

+declare module "react-native-fcm" {
+
+    type FCMEventType = "FCMTokenRefreshed" | "FCMNotificationReceived";
+    export module FCMEvent {
+        const RefreshToken = "FCMTokenRefreshed";
+        const Notification = "FCMNotificationReceived";
+    }
+
+    export module RemoteNotificationResult {
+        const NewData = "UIBackgroundFetchResultNewData";
+        const NoData = "UIBackgroundFetchResultNoData";
+        const ResultFailed = "UIBackgroundFetchResultFailed";
+    }
+
+    export module WillPresentNotificationResult {
+        const All = "UNNotificationPresentationOptionAll";
+        const None = "UNNotificationPresentationOptionNone";
+    }
+
+    export module NotificationType {
+        const Remote = "remote_notification";
+        const NotificationResponse = "notification_response";
+        const WillPresent = "will_present_notification";
+        const Local = "local_notification";
+    }
+
+    export interface Subscription {
+        remove(): void;
+    }
+
+    export class FCM {
+        static requestPermissions(): void;
+        static getFCMToken(): Promise<string>;
+        static on(event: "FCMTokenRefreshed", handler: (token: string) => void): Subscription;
+        static on(event: "FCMNotificationReceived", handler: (notification: any) => void): Subscription;
+        static subscribeToTopic(topic: string): void;
+        static unsubscribeFromTopic(topic: string): void;
+        static getInitialNotification(): Promise<any>;
+        static presentLocalNotification(notification: any): void;
+
+        static scheduleLocalNotification(schedule: any): void;
+        static getScheduledLocalNotifications(): Promise<any>;
+
+        static removeAllDeliveredNotifications(): void;
+        static removeDeliveredNotification(id: string): void;
+
+        static cancelAllLocalNotifications(): void;
+        static cancelLocalNotification(id: string): string;
+
+        static setBadgeNumber(badge: number): void;
+        static getBadgeNumber(): Promise<number>;
+        static send(id: string, data: any): void;
+    }
+
+    export default FCM;
+}