[@azure-tools/cadl-ranch-dashboard] Add Number of Scenarios under each heading

[sarangan12]

Fixes https://github.com/Azure/cadl-ranch/issues/685.

Dashboard after changes:

Cadl Ranch Contribution Checklist:

• [ ] I have written a scenario spec
• [ ] I have meaningful @scenario names. Someone can look at the list of scenarios and understand what I'm covering.
• [ ] I have written a mock API
• [ ] I have used @scenarioDocs for extra scenario description and to tell people how to pass my mock api check.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b84b2ce4849c84274864f4d4402b3e04c3957062

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | --------------------------------- | ----- | | @azure-tools/cadl-ranch-dashboard | Minor |

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