add unique redirect for gallery links

Closes https://github.com/tom-james-watson/old-reddit-redirect/issues/60

A gallery link in the form https://www.reddit.com/gallery/qnjjvh can be
redirected to
https://old.reddit.com/r/OnePiece/comments/qnjjvh/marines_as_shinigami_by_norridzuan_art.
We only have the id to work with, but reddit will actually redirect
https://old.reddit.com/qnjjvh to the full url, so we can just redirect
to that instead.

background.js

@@ -1,5 +1,11 @@
 const oldReddit = "https://old.reddit.com";
-const excludedPaths = ["/gallery", "/poll", "/rpan", "/settings", "/topics", "/community-points"];
+const excludedPaths = [
+  "/poll",
+  "/rpan",
+  "/settings",
+  "/topics",
+  "/community-points",
+];
 
 chrome.webRequest.onBeforeRequest.addListener(
   function (details) {
@@ -11,6 +17,10 @@ chrome.webRequest.onBeforeRequest.addListener(
       if (url.pathname.indexOf(path) === 0) return;
     }
 
+    if (url.pathname.indexOf("/gallery") === 0) {
+      return { redirectUrl: oldReddit + url.pathname.slice("/gallery".length) };
+    }
+
     return { redirectUrl: oldReddit + url.pathname + url.search + url.hash };
   },
   {

manifest.json

@@ -1,7 +1,7 @@
 {
   "name": "Old Reddit Redirect",
   "description": "Ensure Reddit always loads the old design",
-  "version": "1.5.1",
+  "version": "1.6.0",
   "manifest_version": 2,
   "background": { "scripts": ["background.js"] },
   "icons": {