added PluginResults for viewDocument Callbacks
added PluginResults for viewDocument Callbacks

onShow and onClose

sitewaerts/cordova-plugin-document-viewer,sitewaerts/cordova-plugin-document-viewer,sitewaerts/cordova-plugin-document-viewer,bcalvez/cordova-plugin-document-viewer,micaTewe/cordova-plugin-document-viewer,micaTewe/cordova-plugin-document-viewer,bcalvez/cordova-plugin-document-viewer,sitewaerts/cordova-plugin-document-viewer