add license file to the electron sources

Author: Artem

electron-builder.json

@@ -92,6 +92,10 @@
       "to": "defaults",
       "filter": ["**/*"]
     },
+    {
+      "from": "LICENSE",
+      "to": "../LICENSE.redisinsight.txt"
+    },
     {
       "from": "./resources/app",
       "to": "./app",