Edit in JSFiddle

function go() {
  map = L.map("map").setView([47, 2.424], 12);
  var lyrMaps = L.geoportalLayer.WMTS({
    layer: "GEOGRAPHICALGRIDSYSTEMS.PLANIGNV2",
  }, { // leafletParams
    opacity: 0.7
  });
  map.addLayer(lyrMaps);
  var revCtrl = L.geoportalControl.ReverseGeocode({
      collapsed : false,
      resources : ["StreetAddress", "PositionOfInterest","CadastralParcel"],
      delimitations : ["Point", "Circle","Extent"],
      reverseGeocodeOptions : {}
  });
  map.addControl(revCtrl);
}

Gp.Services.getConfig({
  apiKey: "essentiels",
  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;
}