Point CharRNN examples to model files hosted in ml5-data-and-models repo

[bomanimc]

Fixes #1123. Fixes #866.

Community members flagged issues loading models backing the CharRNN examples on the p5.js Web Editor. This issue was occurring because the models, which are JSON files, we're correctly being loaded as assets by p5.js Web Editor. Instead of storing the models in the example, I realized we could also just use the hosted version of this in ml5-data-and-models.

There's a risk in using models in the ml5-data-and-models repo because, should anyone change the directory structure in that repo, our examples would silently break. The benefit, though, is that we don't have to store duplicates of the same sizable model files in every CharRNN example. Longterm, we should probably move these assets to be hosted on a more popular CDN (e.g. AWS S3), but in the meantime, I think this is a good interim solution that fixes the issue.

Verified changes by running the examples locally using npm run develop. I also tested my edit to use the hosted woolf model in p5.js web editor to confirm that it loads and correct the issue highlighted in #1123.

[joeyklee]

LGTM 👍 -- good call on this. Definitely will reduce the size of the repo + it can reinforce the idea that these models are either hosted somewhere remotely or locally and not magic!

[bomanimc]

Opened #1188 to log this conversation about how we host our models!