Added dashboard file and comment-image action

[lydia-rc]

The objective is to automatically comment a dashboard, which tracks the carbon intensity of a resource across multiple builds, as a static image on each pull request.

To complete the dashboard:

• Each time carbon_measure.go runs, append averageKwh and Totalco2perkwh to a csv file
• Keep track of the resources used in a csv
• Replace the placeholder values in each subplot with the columns from a csv

To complete image commenting on PRs:

• Write the dashboard figure as a static image to a folder in .github/data
• Put the link to the raw format of the .github/data folder into comment-image.yml

Additional considerations:

• Storing the images in a .github/data folder might not be a sustainable solution.
• The figure in dashboard.py can be exported as an interactive html file. This could be useful for including the figure in a github page.

[Willmish]

Thanks for opening this @lydia-rc! A good starting point for further visualisation of the action's output