missing instructions to set `nenv shell`; bundle exec with a Node-dependent setup won't pick up `.node-version` file

[jasonfb]

One of the confusing parts of adoption is that during installation, although we are directed to add the loader to ~/.zshrc, there is no direction to set the shell node environment.

In particular, this becomes confusing after you have just successfully installed a node version, because the operating system instructs you that you don't have node installed and you should install it. If no shell version is selected for nenv, I would suggest that nenv detect this and intercept the OS's message and instruct the user to set the shell version using nenv shell 18.9.0

You'll note that this affects you if you are running a command that calls node by proxy, as I don't think the shim works either. For example, even though a .node-version file exists in my repository, it has no effect on the following command:

jason@Jasons-MacBook-Air MyGreatApp % bundle exec rails webpacker:install
sh: node: command not found
sh: nodejs: command not found
Node.js not installed. Please download and install Node.js https://nodejs.org/en/download/

this is somewhat annoying becuase even though I have set a .node-version file with version 18.9.0, it still doesn't pick it up here and there is no indication that the next step is to not follow these instructions and instead run nenv shell 18.9.0