create `package.json` and enable `npm install`

[Mithgol]

The jQuery Plugin Registry is in read-only mode and does not accept new plugin releases.

That registry's web site http://plugins.jquery.com/ recommends moving jQuery plugins to npm and references instructions for publishing to npm.

ElevateZoom's authors should follow those instructions.

[zeitiger]

I published a scoped package to npm until @elevateweb publish. https://www.npmjs.com/package/@zeitiger/elevatezoom