This commit adds Workspaces to the list of data types that can be synced.
This introduces the following changes:
- Adds a new preference `services.sync.engine.workspaces` to control syncing of Workspaces.
- Updates the `syncChooseWhatToSync.js` and `syncChooseWhatToSync.xhtml` files to include the new Workspaces option in the UI.
- Adds relevant localization strings to `preferences-ftl`.
- Updates CSS styling for the Workspaces option.
- Updates `zen-browser.js` to disable Workspace syncing by default.
This change allows users to choose whether to sync their Workspaces across devices.
