This library is intended for use during release to sign packages which
are then served from pkgs.tailscale.com.
The library is also then used by clients downloading packages for
`tailscale update` where OS package managers / app stores aren't used.
Updates https://github.com/tailscale/tailscale/issues/8760
Updates https://github.com/tailscale/tailscale/issues/6995
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
