fix(release): build updates.json with top-level XPI URL

Remove '/releases/<version>/' from update_link; artifacts are uploaded to the base directory (e.g. https://add-ons.jordanwages.com/archive-org-link-grabber/<xpi>). Update example accordingly.

releases/updates.json

@@ -19,6 +19,15 @@
               "strict_min_version": "91.0"
             }
           }
+        },
+        {
+          "version": "0.3.0",
+          "update_link": "https://add-ons.jordanwages.com/archive-org-link-grabber/releases/0.3.0/abf5f9638af544919be4-0.3.0.xpi",
+          "applications": {
+            "gecko": {
+              "strict_min_version": "91.0"
+            }
+          }
         }
       ]
     }