Add ability to download Blob files

[iccub]

Basically we need to take implement this from FF

https://github.com/mozilla-mobile/firefox-ios/blob/master/Client/Frontend/Browser/DownloadContentScript.swift

This is blocked until #1289 is merged

[majd-asab]

Hey @iccub, I'm new to brave & iOS, but I think I can work on this.
Is there anymore background info on this issue? (e.g how is this going to be tested...etc)

[iccub]

@majd-asab everything is the ticket.
You would basically just need to see how Firefoxes handles it and port the solution over to our project

And then find a website or two to test it so our QA team can verify it on their side too.

[Miyayes]

+1 from bitFlyer's team, where there is a use case for blob files. @kylehickinson