Support Extension free URLs

Support for URL(s) without an extension

Main changes

• Support for saving files on your filesystem with extensions even if the url doesn't have an extension
  This means your URLs on excel file can be like http://digitale.bnc.roma.sbn.it/tecadigitale/img/giornale/TO00181645/1935/unico/00000006/original
• Extension will be retrieved from mime-type / Content-type header from the http response
• Avoid over writing the existing files if there are multiple urls with the exact same path
  Existing files will be reported as errors on the final report as well

And some developer debts are payed

• Get rid of optional chaining plugin of babel, since its included in the core modules of babel
• Update browserlist to reduce the number of polyfills added to the bundle
• Reactivate codefactor for quick automatic code review support
• And as always update some dependencies (webpack, babel, electron, jest etc.)