npm installation issue.

Hi! Thank you for this useful pacakge :)

When I'm trying to install a package via npm (npm i highcharts-rounded-corners), there is 404 code for Highcharts dependency:

`
npm ERR! code E404
`
`
npm ERR! 404 Not Found: Highcharts@>=3.0.0
`

So, is there anything I can do to install this package?

Reproduce the reported failure with `npm i highcharts-rounded-corners` and inspect how the package declares its Highcharts dependency. Done means the package installs successfully without the `Highcharts@>=3.0.0` 404 error.

Written by the indexing model from the issue text.