Describe how to use VSCode SSH Remote on IHEP server

[Remco de Boer]

It seems to be possible to use the VSCode extension Remote - SSH on the IHEP server. This could previously only be used if the administrator installed a remote server first. As opposed to the SSH FS extension, this Remote SSH provides full language support and support for other features like source control.

There's only one trick that needs to be applied: put the .vscode-server on a readable path and relink it to the home folder with a symlink. This is to avoid read-write problems.