Remove deprecated JS packages and get rid of vulnerability messages for dash-uploader 0.7.0

A long time has gone from the early days of dash-uploader (there might something in the package.json even from the early 2018 from dash-resumable-upload).

The JS word changes fast, and it would be time to:

• Remove any dependencies in package.json that are not needed
• Update / change any dependencies of deprecated packages
• Update any package with known security issues, if fix available.

I think this should be handled before the release of the dash-uploader 0.7.0, which aims to fix many other things, too.

I'm not a front-end expert myself, so it probably will take me some time to clean the package.json. If anyone else here is more familiar with JS, and would like to take a look, please read this to get started!