Added Tailwind-like colour names

This package now also provides Tailwind-like class names for the colours, along side the Nord colours.

e.g bg-nord0 === bg-nord-0

Support Tailwind 2.0

v1.2.0

1.2.0

Readme edits

Added a link through to the Nord documentation regarding the colour names.

1.0 release

so npm doesn't shout about not being a major version.