Using new FileSystem API to save file without downloading

[leumasme]

A new FileSystem Access api is currently Drafted. This new API allows a site to modify a File on the File System, which would significantly improve the current saving system: Saving would silently overwrite the file instead of having to download it every time. Moving to using this API in the future would be worth looking at in the future for a smoother User Experience. The W3C draft can be found here, the functions are already implemented in Chromium: https://wicg.github.io/file-system-access/#api-filesystemhandle

[leumasme]

A demo of this working can be found here: https://googlechromelabs.github.io/text-editor/