Display list of features on homepage ('Why use AntennaPod')

**Short description**: A feature list that describes what AntennaPod is (project characteristics) and can do (technical functionality). Main features should be visible on the homepage, a full list on a dedicated features page.

**Location**: Homepage and a dedicated 'Features' page.

**Why have this**: To showcase to potential new users/contributors that AntennaPod really is a cool product!

**More info**:
* 'Features' I think should include both technical features (functionality) and characteristics (e.g. respectful of your privacy)
* Each feature should be a title, and optionally a graphic or icon. When clicking on it, it should display a short description (1-2 sentences), with a 'more info' link if there's a relevant entry in our documentation.
* The 'chips' to represent features could be similar to the ones used for blog posts (varying in height).
* It'd be great if we could create a collection, with one `md` file per feature.
* We should be able to indicate a priority, where only the top 7 (?) appear on the homepage.
* We used to have a feature list on the previous homepage :-)