Adopt the Scorecard Action to monitor the project's security posture

[pnacht]

Hey, it's Pedro and I'm back (see #7594 and my colleague Joyce's #7541 and #7546) with another security suggestion.

Joyce and I detected these issues by using the OpenSSF Scorecard, which scans a repository looking for code or settings that can be changed to improve a project's supply-chain security. It is available as a GitHub Action which routinely runs on the repo and adds actionable suggestions directly to the project's Security Dashboard. It can therefore warn you if any change unintentionally weakens the project's security posture.

For the record, RxJava's current score is 8.5/10, which is awesome! In fact, it's in the top 0.1% of popular projects!