yggdrasil: package is not usable after installation

Yggdrasil package doesn't work after installation.

1. It requires a config file /etc/yggdrasil.conf. If the file does not exist, Yggdrasil fails with a panic:

panic: open /etc/yggdrasil.conf: no such file or directory

goroutine 1 [running]:
main.readConfig(0xc000018739, 0xc00001ebc0, 0xc00001873a, 0x2)
        github.com/yggdrasil-network/yggdrasil-go/cmd/yggdrasil/main.go:57 +0xa25
main.main()
        github.com/yggdrasil-network/yggdrasil-go/cmd/yggdrasil/main.go:190 +0x2058
panic: open /etc/yggdrasil.conf: no such file or directory

To fix this error, one must generate a config file with

yggdrasil -genconf > /etc/yggdrasil.conf

2. If the config file exists, but there is no tun kernel module loaded, Yggdrasil fails with a panic:

2021/04/22 10:19:34 Starting multicast module
panic: CreateTUN("\x00") failed; /dev/net/tun does not exist

goroutine 13 [running]:
github.com/yggdrasil-network/yggdrasil-go/src/tuntap.(*TunAdapter).setup(0xc000180000, 0xc0000b4768, 0x4, 0xc0001a8060, 0x27, 0xc0001affff, 0x27, 0xde5bce62a50f7ea0)
        github.com/yggdrasil-network/yggdrasil-go/src/tuntap/tun_linux.go:19 +0x2dc
github.com/yggdrasil-network/yggdrasil-go/src/tuntap.(*TunAdapter)._start(0xc000180000, 0xc00002b7a8, 0x56031243b49e)
        github.com/yggdrasil-network/yggdrasil-go/src/tuntap/tun.go:165 +0x438
github.com/yggdrasil-network/yggdrasil-go/src/tuntap.(*TunAdapter).Start.func1()
        github.com/yggdrasil-network/yggdrasil-go/src/tuntap/tun.go:138 +0x35
github.com/Arceliar/phony.Block.func1()
        github.com/Arceliar/phony@v0.0.0-20210209235338-dde1a8dca979/actor.go:80 +0x31
github.com/Arceliar/phony.(*Inbox).run(0xc0001a0188)
        github.com/Arceliar/phony@v0.0.0-20210209235338-dde1a8dca979/actor.go:89 +0x3f
created by github.com/Arceliar/phony.(*Inbox).restart
        github.com/Arceliar/phony@v0.0.0-20210209235338-dde1a8dca979/actor.go:121 +0x45

To fix this error, a user must load the tun module manually:

modprobe tun