Add IPv6 support in documentation

[Phiwatec]

If anyone needs IPv6 support, you can simple exchange "http://jetbrains-ppa.s3-website.eu-central-1.amazonaws.com"
for "http://s3.dualstack.eu-central-1.amazonaws.com/jetbrains-ppa" within the apt list config. I have tested it and it works perfectly. This could maybe be added to the documentation, as more and more cheap cloud-servers don't have a v4 address.
Greetings