Adds react-dom and react-native as optional peer dependencies

[arcanis]

This diff adds react-dom and react-native as optional peer dependencies.

The react-redux package currently published doesn't list them, which is invalid. For example, here's what Yarn v2 is throwing:

Optional peer dependencies are supported by all three package managers and will silence warning that would otherwise appear if a consumer was omitting them.

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[timdorr]

See these PRs:

#1261
#1282
#1371
#1366

[timdorr]

Whoops, this is actually a dupe of #1390

[arcanis]

@timdorr I'm about to merge a PR in Yarn to make peerDependenciesMeta imply peerDependencies (only for Yarn). This should make it possible to remove the warning in both Yarn and npm. Would that be acceptable?

[timdorr]

If we can leave it out of peerDeps still, that would be great!

The concern I have is for those that haven't yet upgraded their client. npm 6.11 has only been bundled with node for a few weeks now and obviously isn't available on an LTS release yet. For those users, adding the peerDep would make it warn on install.