Although nvm does not officially support .node-version yet
(See nodejs/version-management#13, nodejs/version-management#21), you can use a .node-version with nvm like this:
ln -s .node-version .nvmrc
This works because, .nvmrc supports the .node-version syntax (with an without the v prefix). So .nvmrc is a superset of .node-version.
If one is careful to follow the .node-version specification here, a symbolic link from .node-version to .nvmrc is a good solution until nvm officially supports it.
BTW: volta-cli/volta#983 is considering support of .node-version and referenced this repo.