Upgrade to webtorrent v2 (avoid downloads in RAM)

[ddelange]

Main advantage of webtorrent v2: it uses local storage as opposed to keeping the complete files in memory.

This is more scalable in terms of file size, and allows users to upload entire folders (with nested structure) to a receiver-specified local folder. Currently blaze is limited to a flat list of files going to the browser downloads.

Started the discussion here: #174 (comment)

Potential implementation elaborated here: webtorrent/webtorrent#2849

[ddelange]

@blenderskool do you wish to track the 'entire folder upload' / 'receiver selects download destination' feature in a separate issue?