This is a WordPress plugin. However, /js/map.js will work independently if leaflet.js is loaded. Check readme.txt for WordPress info.

  <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" />
  <script src="https://unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>
  <script src="https://github.com/anewholm/geo-hcard-map/blob/master/js/map.js"></script>

This will create an OpenStreetMap of markers in the div#geo-hcard-map based on hCard markup in the page. Check readme.txt for more info and an example.