RisingWave Download Metrics

• index.html provides the dashboard. You may test it by uncommenting test_data inside, then open index.html. It just uses charts.js.
• The git branch data contains the data files. Please don't push to it manually, unless you know what you're doing.
• We use github actions, see .github/workflows/update-counts.yaml for workflow steps.
• update_data.py is used to update the counts.json file in the data branch. Used in the actions workflow.