PROCESS CHANGE: provide digital contribution badges

Things to include with your process proposal (delete this text):

* Expected benefits. Who gains the benefits? Why will they benefit?
* Expected costs. Who bears the costs? How heavy are they?
* Timeframe for implementation / rollout.
* Are you willing to drive the process, or is this a request for help?

It would be interesting if we provided contribution badges based on the number of contributions an individual has made to Knative. For example, "Knative Contributor Level 1" could be making a single contribution, level 2 could be 10, level 3 could be 50 or 100, and so on.

## Expected Benefits
This would help to encourage contributor growth, and help convert contributors who only make a few contributions into longer term contributors. A lot of contributors to open source projects do so for professional growth, so by providing them with public recognition (e.g. on their LinkedIn profile with a badge) we will be appealing to their interest. By providing multiple levels of the badge, we can encourage contributors to continue contributing beyond their first few contributions to the project and to "level up" their badge.

## Expected costs
We would need to pay for some platform like Credly. Perhaps we could get access to the CNCF account that is used to create badges for talks at conferences?

## Timeframe
One option would be to check this manually and periodically send the badges out ourselves. Another option would be to use the API for the platform we choose (such as Credly) to automatically send them. We could create a GitHub action that runs periodically and checks contributions, then sends new badges to the email associated with the account.

I would be happy to build the GitHub action or help drive this project in whichever direction is decided