Implement Extensions System

[LeNitrous]

Base implementation for extensions. Closes #251.

[sr229]

You might wanna document how VFS is used to provide filesystem access to the host in Vignette.

[LeNitrous]

VFS is a part of Stride. They have documentations for it on their end.

[sr229]

VFS is a part of Stride. They have documentations for it on their end.

We're not talking about the VFS, we're talking about how we use it. Is this still in-line with our spec in #251?

[LeNitrous]

For the most part yes specially with handling of the metadata.

However, I've taken a few liberties in the scripting API and loading the entry point script. A minimal working example is basically an ES6 Javascript file with two exports named activate and deactivate respectively. Additionally, the developer can access the core by importing the vignette module.

import { vignette } from "vignette";

export function activate() { }

export function deactivate() { }

This PR is only the bare minimum and does not fully implement the specification. Other parts of the API will be added in different PRs at a later time after consideration and discussion.

[sr229]

We'll do a proper RFC to further standardize this so we don't end up in dev hell. Otherwise, LGTM for a initial build.