fixed error in selecting path and naming screenshot

package.json

@@ -4,7 +4,8 @@
     "description": "tool for documenting online harassment",
     "main": "main.js",
     "dependencies": {
-        "electron": "^1.7.10"
+        "electron": "^1.7.10",
+        "eslint": "^4.15.0"
     },
     "devDependencies": {},
     "scripts": {

renderer.js

@@ -1,7 +1,9 @@
 const electron = require('electron');
+const remote = electron.remote;
 const desktopCapturer = electron.desktopCapturer;
 const electronScreen = electron.screen;
 const shell = electron.shell;
+const dialog = remote.dialog;
 
 const fs = require('fs');
 const os = require('os');
@@ -16,7 +18,12 @@ var screenshotPath = '';
 var caseName = '';
 
 pathButton.addEventListener('click', function(event) {
-    dialog.showSaveDialog(function(fileName) {
+    dialog.showSaveDialog({
+            filters: [
+                { name: 'png', extensions: ['png'] }
+            ]
+        },
+        function(fileName) {
             if (fileName === undefined) {
                 return;
             }