Show scrollbars on Linux/Windows

[warpdesign]

Current version of React-Explorer uses overlayScrollbars which are hidding big ugly scrollbars on Windows/Linux. Problem scrollbars seem to be hidden and using touchpad to scroll does not seem to make them appear.

Using SimpleBar could be a good idea.

Also, the overlayScrollbars of Chrome was removed in Chrome 78 so will likely be removed from Electron as well.

[warpdesign]

After some experiments it won't be that easy to use SimpleBar (or react-custom-scrollbars) since React-Explorer is using AutoSizer+Table (which itself uses Grid) all from React-Virtualized.

Saw hacks hooking into the onScroll event to position the grid but performance really suffers and it's not easy to implement.

Alternative: using css-only solution overflow: overlay. For example:

body {
  overflow: overlay;
}

 ::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-thumb {
  background: rgba(90, 90, 90, .3);
  border-radius:5px;
}

::-webkit-scrollbar-track {
  background: rgba(0, 0, 0, 0);
} 

Only drawback is that the scrollbar won't auto hide.

[warpdesign]

Elements that need to be scrollable:

• Dialog
• FileTable
• Favorites

[warpdesign]

Fixed in #110