Refactor in a modular way

Hello @jcubic ,

Thanks for this wonderful software. I am excited when trying the features of this git in browser framework.
I do have suggestions from a user and an app developer perspective.

I'm planning to use this project as a framework for my note taking app. Using git to keep notes, and sync among devices.

It will be easier for me to use a modular system. Say the base system is only with browserfs, and a limited set of basic commands to install other apps.

1. vi and emacs can be different apps, expose some API and commands.
2. git can be another app, expose API and commands.
3. people can use the framework to develop other apps, as long as there is a spec on how to use the commands exposed by other apps.

Thanks again for your effort on building the software and supporting me exploring it.

BR,Austin