“Premium” section for paid apps above certain price

## Problem

There's a reputation that AppCenter apps are “all” handy little utility apps. While these apps may be the most common, we could do better to expose the larger, more complex apps like Akira, Sequeler, Ensembles, etc.

## Proposal

A decent signifier for these types of apps is the suggested price the developer set. But if we're using price as the signal, we should ensure we're using price as the user-facing identifier to avoid weird conflicts (e.g. if we called these something actually meaning "complex" apps, it would be weird to see a simple but expensive app show up).

So, we could add a section of “Premium” apps where the price is $10 or higher. This could also have a trickle down effect of encouraging higher suggested prices for apps to get into the premium section, which I don't think is a bad thing; but we can always make adjustments if we see things shifting in a direction we don't want.

## Prior Art

The Google Play Store and Apple’s App Store have sections like “Top Paid” apps, and at least Google Play has a “premium apps” section which appears to just be… any paid app? It’s not clear.