$cssPlugins = ['prism/prism.css',
               '//unpkg.com/leaflet@1.3.1/dist/leaflet.css' => ['integrity' => 'sha512-Rksm5RenBEKSKFjgI3a41vrjkw4EVPlJ3+OiI65vTjIdo9brlAacEuKOiQ5OFh7cOI1bkDwLqdLw3Zg0cRJAAQ==',
                                                                'crossorigin']];