Edit in JSFiddle

function go() {
  map = L.map("map").setView([47, 2.424], 12);
  var lyrMaps = L.geoportalLayer.WMTS({
    layer: "GEOGRAPHICALGRIDSYSTEMS.MAPS.SCAN-EXPRESS.STANDARD",
  }, { // leafletParams
    opacity: 0.7
  });
  map.addLayer(lyrMaps);
  var searchCtrl = L.geoportalControl.SearchEngine({});
  map.addControl(searchCtrl);
}

Gp.Services.getConfig({
  apiKey: "jhyvi0fgmnuxvfv0zjzorvdn",
  onSuccess: go
});

var infoDiv = document.getElementById("info");
infoDiv.innerHTML = "<p> Extension Leaflet version " + Gp.leafletExtVersion + " (" + Gp.leafletExtDate + ")</p>";
<div id="map"></div>
<div id="info"></div>
#map {
  padding: 5px;
  width: 100%;
  height: 500px;
  box-shadow: 0 0 10px #999;
}

#info {
  padding: 5px;
  width: 100%;
  height: 20px;
  font-family: monospace;
}