Support for v2 and hybrid torrent files

[past-due]

See: https://blog.libtorrent.org/2020/09/bittorrent-v2/

v2 moves to SHA-256 hashes. It is possible to create hybrid torrents that support v1 and v2 swarms at the same time.

SHA-1 chosen-prefix attacks are now in the USD 10k-100k range.

Reference: pobrn/mktorrent#29 (comment)

Given all of the above, I think there'd be a great benefit to supporting v2-only, and hybrid torrent file generation (in addition to the current v1-only support).

[rsnitsch]

Thank you very much for making me aware of this. It will be on the top of my TODO list.

[rsnitsch]

Relevant BEPs:
https://www.bittorrent.org/beps/bep_0003.html (v1)
https://www.bittorrent.org/beps/bep_0047.html (padding)
https://www.bittorrent.org/beps/bep_0052.html (hybrid/v2, which requires padding according to BEP 47)