Add filter for themes with Front Page template

### What

I would love to see either a specific `feature:` filter or some form of theme tag implemented to categorize block themes that include a _Front Page_ template.

### Why

The _Front Page_ template can make it simpler to create a unique looking homepage, but some users may not want to have to rely on a separate template for that page. For themes that come with the _Front Page_ template, it cannot be deleted, so it has to be used in some capacity.

Adding a filter or tag would make it easier for customers to find the kind of theme they're looking for (if they want a specific template for their homepage), or confirm whether a theme they're interested in requires the use of the _Front Page_ template _before_ activating it. At present, there's no way to know whether themes include that template except by activating themes one by one and checking the template list in the Site Editor for each.

### How

_No response_

No file, test, or entry point is identified. Start by locating the existing theme catalog filters and the metadata or API that exposes theme templates, then determine whether a filter or tag best fits the current design. Done means customers can identify themes with a Front Page template before activating them, with coverage for the available theme data.

Written by the indexing model from the issue text.