firefox: add sidebar.revamp and allow unloading Sidebery

conf/firefox-forbidden-policies.js

@@ -75,5 +75,8 @@ lockPref("security.ssl.enable_ocsp_must_staple", true);
 // ECH, which is otherwise the default=
 lockPref("security.tls.ech.grease_http3", true);
 
+// New sidebar
+lockPref("sidebar.revamp", true);
+
 // No making configuration on the last line of the file!
 //

etc/firefox/policies/policies.json

@@ -171,7 +171,7 @@
       },
       "{3c078156-979c-498b-8990-85f7987dd929}": {
         "install_url": "https://addons.mozilla.org/firefox/downloads/latest/sidebery/latest.xpi",
-        "installation_mode": "force_installed"
+        "installation_mode": "default_installed"
       },
       "{446900e4-71c2-419f-a6a7-df9c091e268b}": {
         "install_url": "https://addons.mozilla.org/firefox/downloads/latest/bitwarden-password-manager/latest.xpi",
@@ -729,6 +729,12 @@
         "Type": "boolean",
         "Value": true
       },
+      "sidebar.revamp": {
+        "Comment": "Preference not allowed for stability reasons.",
+        "Status": "default",
+        "Type": "boolean",
+        "Value": true
+      },
       "ui.systemUsesDarkTheme": {
         "Comment": "Another defaulting to dark theme.",
         "Status": "default",