Add Typescript definitions (#225)

* Add Typescript definitions

* Fix typescript definition

index.d.ts

@@ -0,0 +1,17 @@
+import * as React from 'react';
+import { ViewStyle } from 'react-native';
+
+export interface BlurViewProperties {
+  blurType: 'xlight' | 'light' | 'dark'
+    // tvOS only
+    | 'extraDark' | 'regular' | 'prominent';
+  blurAmount?: number; // 0 - 100
+  style?: ViewStyle;
+}
+
+export class BlurView extends React.Component<BlurViewProperties, {}> {}
+
+
+export interface VibrancyViewProperties extends BlurViewProperties {}
+
+export class VibrancyView extends React.Component<VibrancyViewProperties, {}> {}