React >17 used in extension SDK, but latest npm package release requires react 16

[brettguenther]

The extension sdk repository was updated to react 17, but there are dependencies in this repo still requiring react 16. As one example, looker/icons still has a react 16 peer dependency in the latest npm release 1.5.21

This causes issues when leveraging both looker packages (as an example, it is currently an issue in the create-looker-extension repo)

[CaptainN]

It looks like a PR was merged - how do we get this released to npm registry?