Add "module" to package.json build for ES modules

[JohnHardy]

Please would it be possible to add a module field in the package.json for an ES2019 bundle?

https://github.com/rollup/rollup/wiki/pkg.module

At the moment it seems like only browser and main are supported, targeting UMD and CommonJS respectively?

At the moment we are using rollup and the line that causes the trouble in bundling (using the commonJs() rollup plugin) is this one:

msgpack-javascript/src/utils/utf8.ts

Line 2 in c969bc9

process.env.TEXT_ENCODING !== "never" && typeof TextEncoder !== "undefined" && typeof TextDecoder !== "undefined";

[gfx]

Thanks for the feature request. Sounds a good idea, so I'll do in the next few releases.