Add package metrics and health to readme.md

[rogeralsing]

I just saw this lib https://github.com/BEagle1984/silverback They have some nice quality and download badges in their readme. We should add the same things for our readme here.

[SeanKilleen]

Adding some details in case they're helpful.

• The quality metrics in the README are surfaced from sonarcloud.io. Would need to import the repo(s) and set it up which requires permissions.
• Shields.io provides some of the other badges: https://shields.io
• I believe GitHub actions has badges for any use of GitHub Actions etc.
• I'm not sure test coverage stats are available OOTB with GitHub actions. CodeCov.io, Coveralls, or a similar service could probably provide these stats which could then be brought in via a shields.io badge or similar.