Multi-install / Folder install

### Problem

I tend to keep a folder of .flatpakrefs that I share between OS installs. Currently I install them one at a a time, whether that be through Terminal or clicking them to open side load itself.

### Proposal

I would like to be able to drag and drop a folder to mass install, or point it to a folder to watch for installer files. Even adding a flag to be able to mass install them in Terminal would be great.

This will just streamline my reinstalls OR if I was in another OS, then my elementaryOS install could be watching for what I install there and install it here though the folder watching.

I realize there are some very different solutions proposed. Just tried to think of the different ways this could be tackled to save the clicks.

### Prior Art (Optional)

A good example of this would be mass unzipping/untaring everything in a folder.