Add web app manifest file

CHDataManagement/Views/Settings/Pages/PageSettingsDetailView.swift

@@ -57,6 +57,11 @@ struct PageSettingsDetailView: View {
                     selectedFile: $pageSettings.imageCompareJsFile,
                     allowedType: .code)
 
+                FilePropertyView(
+                    title: "Web App Manifest File",
+                    footer: "The manifest file with the properties of the website when used as a progressive web app",
+                    selectedFile: $pageSettings.manifestFile)
+
                 LocalizedPageSettingsView(settings: pageSettings.localized(in: language))
                     .id(language)
             }