add template variable `{filename-extension}`

src/core/bg/config.js

@@ -60,7 +60,7 @@ const DEFAULT_CONFIG = {
 	loadDeferredImagesKeepZoomLevel: false,
 	loadDeferredImagesDispatchScrollEvent: false,
 	loadDeferredImagesBeforeFrames: false,
-	filenameTemplate: "{page-title} ({date-locale} {time-locale}).html",
+	filenameTemplate: "{page-title} ({date-locale} {time-locale}).{filename-extension}",
 	infobarTemplate: "",
 	includeInfobar: !IS_NOT_SAFARI,
 	confirmInfobarContent: false,

src/ui/pages/help.html

@@ -890,6 +890,7 @@
 					<li><code>{digest-sha-384}</code>: the SHA-384 hash value of the entire page content</li>
 					<li><code>{digest-sha-512}</code>: the SHA-512 hash value of the entire page content</li>
 					<li><code>{profile-name}</code>: the name of the profile used to save the page</li>
+					<li><code>{filename-extension}</code>: the extension of the filename depending on the file format (i.e. "html", "u.zip.html", "zip.html", "zip")</li>
 				</ul>
 			</li>
 			<li>