Added drag/drop functionality to the add mods button.

You can now drag one or more files onto the add mods button in order to add them to the mods directory. Only jar, litemod, and zip files will be moved.
Changed eslint to use a single configuration file, with overrides for the UI scripts.
Now using fs-extra, replace usages of rimraf and mkdirp with fs-extra functions.

app/assets/css/launcher.css

@@ -1545,13 +1545,15 @@ input:checked + .toggleSwitchSlider:before {
     margin-bottom: 10px;
 }
 #settingsDropinFileSystemButton:hover,
-#settingsDropinFileSystemButton:focus {
+#settingsDropinFileSystemButton:focus,
+#settingsDropinFileSystemButton[drag] {
     background: rgba(54, 54, 54, 0.25);
     text-shadow: 0px 0px 20px white;
 }
 /* Refresh instructions on the file system button. */
 #settingsDropinRefreshNote {
     font-size: 10px;
+    pointer-events: none;
 }
 
 /* Button to remove drop-in mods. */
@@ -2663,7 +2665,6 @@ input:checked + .toggleSwitchSlider:before {
     box-shadow: 0px 0px 10px 0px rgb(0, 0, 0);
     overflow: hidden;
     position: relative;
-    /*background-image: url('https://cdn.discordapp.com/avatars/169197209630277642/6650b5a50e1cb3d00a79b9b88b9a0cd4.png');*/
     background-position: center;
     background-repeat: no-repeat;
     background-size: contain;