Add auto label to read version from .node-version

[shadowspawn]

Pull Request

Problem

People would like to be able to specify the target version in a file, and have it read by their preferred node version manager. The commonly used generic filename is .node-version.

Reference: nodejs/version-management#13

Solution

Read version number from .node-version and parse as if it had been given on command line. Be lenient with line endings, as I proposed in nodejs/version-management#13

Use the label auto, as used by nvs for this purpose.

[shadowspawn]

(Errata: I included the version bump and changelog entry in this PR, which should not normally be included.)

[shadowspawn]

Released in n 6.5.0.

[shadowspawn]

Somewhat related issues: #150 #423 #547 #573

[ljharb]

This was a very very bad idea to merge and publish prior to getting agreement between version managers. By doing this, you'd likely poisoned .node-version forever from ever getting consensus among version managers or the node version management working group.

[shadowspawn]

Well @ljharb , years have gone by since discussions started and there were already multiple other implementations using .node-version: nvs, avn, nodenev, direnv, and asdf-nodejs.

I wanted to try the ideas for real, and the current implementation is consistent with the lowest common denominator discussed in the working group. I thought it was a pretty safe bet.

If the working group decides on something else, then I can change to follow.

[ljharb]

There is never a safe bet, whether it takes weeks or decades, to "try out" a potential standard.

[shadowspawn]

Re-released using filename .n-node-version in n 6.5.1.

I look forward to seeing if there is any consensus on the potential standard.