Update chroot.md with network requirement hint for xchroot

[kardwen]

When following the Installation via chroot guide, I encountered the small issue that xchroot would return the message special device /etc/resolv.conf does not exist. I thought that maybe a hint indicating to ensure that a network connection is configured might clear this up.

[classabbyamp]

would probably be better to add this note earlier, as more than just xchroot in that guide would need network

also separately: it might be good to make xchroot not fail hard if resolv.conf doesn't work

[kardwen]

I actually used void-installer and then skipped to https://docs.voidlinux.org/installation/guides/chroot.html#configuration to install Limine as my bootloader because it does not require an additional partition like GRUB does for GPT partitioned disks on BIOS. Because I rebooted into the live environment for some reason and forgot to reestablish my network connection, I ran into the described issue.