Add isIndeterminate to ProgressViewProps (#140)

Co-authored-by: Jesse Katsumata <jesse.katsumata@gmail.com>

Author: koloboid

js/index.d.ts

@@ -32,6 +32,10 @@ export type ProgressViewProps = ViewProps & {
    */
   trackImage?: ImageSourcePropType,
 
+  /**
+   * Turns the progress bar into an indeterminate progress bar
+   */
+  isIndeterminate?: boolean,
   accessibilityLabel?: String,
 };
 export class ProgressView extends React.Component<ProgressViewProps> {}