docs: deploy docs using netlify (#4774)

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, fixes #4609.

build/netlify-docs.js

@@ -0,0 +1,19 @@
+const sh = require('shelljs');
+
+const GIT_CONTAINS = `git tag --contains ${process.env.COMMIT_REF}`;
+
+const output = sh.exec(GIT_CONTAINS, {async: false, silent:true}).stdout;
+
+// if we're on master branch and not on a tagged commit,
+// error the build so it doesn't redeploy the docs
+if (process.env.BRANCH === 'master' && output === '') {
+  process.exit(1);
+
+// if we're on any other branch, we can regenerate docs
+} else {
+  // generate the docs
+  sh.exec('npm run docs:api');
+
+  // copy the legacy docs over
+  sh.cp('-R', 'docs/legacy-docs', 'docs/api/docs');
+}