[Feature request] Support for preferDev as a package attribute

[kunagpal]

I'm opening this issue because:

• npm is crashing.
• npm is producing an incorrect install.
• npm is doing something I don't understand.
• Other (see below for feature requests):

What's the feature?

The existence of preferDev in a module's package.json will raise warnings when the module is being installed as a dependency instead of a devDependency.

What problem is the feature intended to solve?

This will help prevent adding packages like eslint, mocha, etc to dependencies accidentally.

Is the absence of this feature blocking you or your team? If so, how?

No, this feature is meant to be a usability improvement.

Is this feature similar to an existing feature in another tool?

Not that I know of.

Is this a feature you're prepared to implement, with support from the npm CLI team?

Yes

[kunagpal]

Ping...