Add root certificate to Linux.md

Obtain CA certificate (DC root certificate) from https://my-domain-controller/certsrv/certcarc.asp

You will get certnew.cer

Centos etc (rpm based)

Copy certificate (.cer) to /etc/pki/ca-trust/source/anchors/

update-ca-trust
systemctl restart docker

Ubuntu/Debian (deb based)

Change certificate's (certnew.cer) extension to .crt and copy it to /usr/local/share/ca-certificates/

update-ca-certificates
systemctl restart docker