Add offline fallback

[asacolips]

Currently, this library loads its Vue and Vuex dependencies via CDN, which is great for performance and online play, but that's problematic if either those CDNs are unavailable, or if Foundry is running in offline mode (e.g. on poor wifi at a convention or running on a gaming table/LAN at home during an internet outage).

Ideally, VuePort would fallback and use a version of those libraries stored in the module itself if it's unable to load via CDN.

[kakaroto]

Vueport uses dlopen for loading the dependencies, and the dlopen module had a caching for local use feature planned which I never got around to doing. See :
https://github.com/ForgeVTT/fvtt-module-dlopen/tree/master/cache
https://github.com/ForgeVTT/fvtt-module-dlopen/blob/master/dlopen.js#L4

The idea was, on first load (supposedly when you install the module, you have internet and you launch it at the same time), it would pre-fetch all the dependencies and cache them, falling back to them automatically if cdn url fails, or if the option to always fetch from cache is enabled.

So, yeah, known/planned, never implemented due to lack of time, but the feature is meant to go in the other project rather than this one so it benefits anyone using the dynamic dependency loader.

(Note: I transferred the issue to the other repo)