fix(type): add new testID to typescript definition file (#103)

* chore(types) Adds typing for testID on LoginButton
* Update types/FBLoginButton.d.ts

Fixes silly typo

Co-authored-by: Mike Hardy <[email protected]>

Author: doublethefish

types/FBLoginButton.d.ts

@@ -57,6 +57,11 @@ export class LoginButton extends React.Component<{
      * View style, if any.
      */
   style?: any;
+
+  /**
+   * testID, if any.
+   */
+  testID?: string;
 }> {
   static defaultProps: {
     style: typeof styles.defaultButtonStyle;