Add setting for Card Browser column alignment

Anki exposes different column alignment values for the Card Browser via BrowserColumns.Alignment with center alignment the default.

But there is no way for the user to change it. A workaround currently is to use a third-party addon, e.g. Add column alignment option by vwkd · Pull Request #132 · ankipalace/advanced-browser · GitHub But Anki should just offer a setting to the user directly.