Restrict banner filetypes

src/client/app/desktop/api/update-banner.ts

@@ -6,6 +6,20 @@ import ProgressDialog from '../views/components/progress-dialog.vue';
 export default (os: OS) => {
 
 	const cropImage = file => new Promise((resolve, reject) => {
+		
+		var regex = RegExp('\.(jpg|jpeg|png|gif|webp|bmp|tiff)$')
+
+		if(!regex.test(file.name) ) {
+			os.apis.dialog({
+				title: '%fa:info-circle% %i18n:desktop.invalid-filetype%',
+				text: null,
+				actions: [{
+					text: '%i18n:common.got-it%'
+				}]
+			});
+			reject
+		}
+		
 		const w = os.new(CropWindow, {
 			image: file,
 			title: '%i18n:desktop.banner-crop-title%',