Isomorphic npm package

[blenderskool]

The library published on npm works only on the client-side. Support for the pigmnts library on server-side using Node.js can be implemented considering following points:

• pigments_node() function can be implemented that is compatible with Node.js and does not depend on Browser APIs like canvas.
• The existing pigments() function may depend on pigmnts_node() function making it easier to interact with the library on the client-side by abstracting canvas APIs.
• Appropriate build system to create a single isomorphic package. wasm-pack supports multiple outputs targets, but combining them under a single package is a little messy. Hoping for this to be merged rustwasm/wasm-pack#705