Passage de dépendances en option

package.json

@@ -103,7 +103,6 @@
 		"copy-webpack-plugin": "^4.5.2",
 		"css-loader": "^0.28.11",
 		"csv-loader": "^2.1.1",
-		"cypress": "^3.1.0",
 		"daggy": "^1.3.0",
 		"dedent-js": "^1.0.1",
 		"enzyme": "^3.3.0",
@@ -133,7 +132,6 @@
 		"mock-local-storage": "^1.0.5",
 		"nearley-loader": "^2.0.0",
 		"postcss-loader": "^2.1.2",
-		"prerender-spa-plugin": "^3.4.0",
 		"ramda-fantasy": "^0.8.0",
 		"raw-loader": "^0.5.1",
 		"serve": "^10.0.2",
@@ -150,5 +148,9 @@
 		"webpack-pwa-manifest": "^3.6.2",
 		"workbox-webpack-plugin": "^3.6.1",
 		"yaml-loader": "^0.5.0"
+	},
+	"optionalDependencies":{
+		"prerender-spa-plugin": "^3.4.0",
+		"cypress": "^3.1.0"
 	}
 }