nvm - Docker mod for code-server and openvscode-server

This mod adds Node Version Manager to linuxserver/code-server and linuxserver/openvscode-server, to be installed during container start.

In the docker arguments, set an environment variable DOCKER_MODS=linuxserver/mods:code-server-nvm

If adding multiple mods, enter them in an array separated by |, such as DOCKER_MODS=linuxserver/mods:code-server-nvm|linuxserver/mods:code-server-mod2