Fix #1958 - Propagate container list reordering in Firefox menus

Since Fx 123, we have a new API (contextualIdentities.move) that let
us reorder the container list everywhere in Firefox. This patch
looks if the API is supported by the client and propagate the change
if it's the case.

src/js/popup.js

@@ -211,6 +211,11 @@ const Logic = {
   async saveContainerOrder(rows) {
     const containerOrder = {};
     rows.forEach((node, index) => {
+      if (typeof browser.contextualIdentities.move === "function") {
+        browser.contextualIdentities.move(
+          node.dataset.containerId, index);
+      }
+
       return containerOrder[node.dataset.containerId] = index;
     });
     await browser.storage.local.set({