feat: Add preference to focus on urlbar on startup, b=no-bug, c=workspaces

prefs/zen/zen-urlbar.yaml

@@ -32,6 +32,9 @@
 - name: zen.urlbar.show-pip-button
   value: false
 
+- name: zen.urlbar.open-on-startup
+  value: true
+
 # Mark: Zen suggestions controls
 
 - name: zen.urlbar.suggestions.quick-actions

src/zen/workspaces/ZenWorkspaces.mjs

@@ -1020,6 +1020,8 @@ class nsZenWorkspaces {
       delete this._initialTab;
     }
 
+    showed &&= Services.prefs.getBoolPref("zen.urlbar.open-on-startup", true);
+
     // Wait for the next event loop to ensure that the startup focus logic by
     // firefox has finished doing it's thing.
     setTimeout(() => {