[JS Client] Fix for build error in React Native

[kaxline]

There is an issue when adding streamr-client to a React Native project, where the build throws a warning:

warn Package streamr-client has been ignored because it contains invalid configuration. Reason: Package subpath './package.json' is not defined by "exports" in {ProjectRoot}/node_modules/streamr-client/package.json

Which is a problem with the react-native cli discussed a bit here:

react-native-community/cli#1168

I found a fix for it here, which seems like a light fix that could preempt a lot of confusion and FUD by new adopters adding streamr-client to React Native:

https://github.com/infctr/eslint-plugin-typescript-sort-keys/pull/28/files

This PR applies the changes to package.json "exports" that should resolve the error/warning.

Let me know what you think!

[CLAassistant]

All committers have signed the CLA.

[timoxley]

Thanks for this. Note that package.json currently needs the dist in the path which will be rewritten by this script when publishing: https://github.com/streamr-dev/network-monorepo/blob/a336cc3db4f7beb71f1fc78a95aecac642111e4e/packages/client/copy-package.js#L8-L14

[kaxline]

@timoxley Thanks for taking a look! Can you check my latest commit and see if that's what you had in mind?