dillon1000/react

Add publish workflow, triggerable via API request (#20726)

Adds a new CircleCI workflow, which I will use to publish prereleases
(`next` and `experimental`) for a given commit.

The CircleCI API doesn't yet support triggering a specific workflow, but
it does support triggering a pipeline. So as a workaround you can
triggger the entire pipeline and use parameters to disable everything
except the workflow you want. CircleCI recommends this workaround here:
https://support.circleci.com/hc/en-us/articles/360050351292-How-to-trigger-a-workflow-via-CircleCI-API-v2-

Eventually we can set this workflow to trigger on a cron schedule (once
per week, for example).