Assigning copyright to the TVL community (whatever that is), and
adding AGPL-3.0-or-later license.
I also cleaned up some of the stuff on the landing page.
Change-Id: I4dbca19406e00e5105fed50e8fb64e0fcca23e3a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11013
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
