Add jest, spectron and getPort util for tests

Author: th-ch

package.json

@@ -61,7 +61,10 @@
 		"electron-builder": "^22.4.1",
 		"electron-devtools-installer": "^3.0.0",
 		"electron-icon-maker": "0.0.4",
+		"get-port": "^5.1.1",
+		"jest": "^25.5.1",
 		"rimraf": "^3.0.2",
+		"spectron": "^10.0.1",
 		"xo": "^0.29.0"
 	},
 	"xo": {