Add TypeScript definition file (#73)

Author: forabi

typings.d.ts

@@ -0,0 +1,21 @@
+module 'scroll-into-view-if-needed' {
+  interface ScrollIntoViewIfNeededOptions {
+    centerIfNeeded: boolean;
+    duration: number;
+    easing: 'ease' | 'easeIn' | 'easeOut' | 'easeInOut' | 'linear';
+  }
+
+  interface ScrollIntoViewIfNeededFunction {
+    (
+      node: Element,
+      centerIfNeeded: boolean = false,
+      options: ScrollIntoViewIfNeededOptions = {
+        centerIfNeeded: false,
+        duration: 0,
+        easing: 'ease',
+      }
+    ): void;
+  }
+  const ScrollIntoViewIfNeeded: ScrollIntoViewIfNeededFunction;
+  export default ScrollIntoViewIfNeeded;
+}