Add ability so download file

Hi Dan - if you move to the "Files" sidebar - the vertical 3 dots icon next to the filename will offer you the download option.

For text-based files opened in the browser, you can click Ctrl/Cmd-S to save the file to disk.

I never saw this panel before so thanks for that! I still think that on the message itself there should be a more visible way to download the file. 

This is any file that can be opened in the browser, not just XML files. Since the app is basically just a wrapper around a browser window, it acts just like a web browser would. There needs to be some code added to treat every file type (css, js, html, xml, etc) as a download and not an open file.