docs: deploy docs using netlify

[gkatsev]

Description

This adds in the legacy docs into the repo and enables automatic deployment via netlify. The netlify-docs.js script will error out the build on netlify on master if we're not on a tagged commit so that it won't redeploy the docs unless there's a new release. If we're not on master or on master with a tagged commit, it will process with the deploy.
Also, this removes the API docs from being published with npm, fixing #4609.

[gkatsev]

Once this is merged and published, we can change docs.videojs.com from pointing at the github pages to netlify.

[brandonocasey]

Do legacy docs have to be in the repo? or could we pull them down on netlify before deploy?

[brandonocasey]

seems like we should have { and } here

[gkatsev]

um... yes. Forgot to do so.

[gkatsev]

The legacy docs don't strictly have to be here but I think it's easier to just include them and copy them over during the deploy rather than trying to figure out how to download it.

[brandonocasey]

I just think it will add a lot of bulk to the repo during git clone other than that I don't see why we couldn't keep it in the repo. I guess either way is fine, but maybe we should get other opinions.

[misteroneill]

I don't have a problem with this. It will add something to the git clone cost, but I don't think it's a lot. And it's a one-time cost versus adding complexity to the versioning process to download/generate old docs.

Changes LGTM