added labels for clustering

[ggrossetie]

@AlexicaWright could you please revert your changes on package-lock.json?

You also need to fix the following issues:

src/css/labels.css
 112:1  ✖  Unexpected empty line before closing brace   block-closing-brace-empty-line-before
 113:1  ✖  Expected empty line before rule              rule-empty-line-before

Thanks!