Output Granularity for Easier Integration

[Terre8055]

Issue Description: Hello,

I have been using the DeveloperMetrics/deployment-frequency GitHub Action to track deployment frequency metrics. While the Action works well, I have encountered some challenges when trying to integrate the results with other applications, such as Slack or visualization tools

Current Situation:

The Action currently outputs the metrics in a markdown file. To extract specific values, such as deployment frequency results, I need to use additional commands like sed to parse the file. For example:

DEPLOYMENT_FREQUENCY_RESULTS=$(cat "${{ steps.deployment-frequency.outputs.markdown-file }}" | sed -n '/Results:/p' | sed 's/\*\*/\*/g')

Could the outputs be made like this

outputs:
  deployment-frequency: "3.33 per day"
  deployment-frequency-rating: "Elite"
  deployment-period: "30 days"
  active-deployment-days: "4 days"