Add Element Desktop for Mac to App Store

### Your use case

#### What would you like to do?

Introduce non-technical Mac users to Matrix

#### Why would you like to do it?

The only way to communicate via Matrix for users on Intel-based Macs today is via brew, manually downloading and installing a dmg, or via web. The app in the AppStore is only available for M1-based macs. Currently available distribution methods is a non-option for most non- or even semi-technical users.

### Have you considered any alternatives?

* Other clients: None available AFAICT
* brew: not an option for non-technical users
* Manually downloading and installing a dmg: not an option for non-technical users
* Current AppStore app: Not available for Intel Macs or older versions of OS X

### Additional context

Related issue for Windows: vector-im/element-desktop#651

Start with the issue description and the related Windows issue, vector-im/element-desktop#651, to identify the supported Mac targets and current distribution constraints. Done means Element Desktop is available through the Mac App Store for Intel Macs and older supported macOS versions.

Written by the indexing model from the issue text.