chore(package): update electron-builder to version 21.2.0

Closes #139

Author: greenkeeper[bot]

package.json

@@ -82,7 +82,7 @@
     "css-loader": "^1.0.0",
     "devtron": "^1.4.0",
     "electron": "^3.0.0",
-    "electron-builder": "^20.8.1",
+    "electron-builder": "^21.2.0",
     "electron-devtools-installer": "^2.2.0",
     "electron-reload": "^1.2.1",
     "enzyme": "^3.6.0",