Updating mapbox-gl-js plugins

• Each plugin should live in a directory that matches its name + version.
• Each plugin should have an entry in docs/_data/plugins.json with it's directory, version number, and files.

Testing

• npm run test-plugin

Deploying

• Install aws-cli and configure it with credentials.
• Include a directory for your plugin.
• Add entry to docs/_data/plugins.json.
• Update the latest field in docs/_data/plugins.json
• mbx auth {AUTH_CODE}
• Finally, run npm run plugin-deploy.