WIP: Attribution

[trieloff]

This is a generic attribution query that allows you to ask "Which source ortarget of the previous checkpoint happened within an attribution time window that then lead to a conversioncheckpoint with specific sources or targets"

The query will report the most frequent source or target values and their respective conversion rate.

This can be used to see:

• which referrers lead to conversions
• which assets were seen before a button click
• which DOM elements where clicked before a form submission
• which blocks were seen before another block was seen

Other than adobe/helix-rum-enhancer#101 this does not require any client-side changes.

[github-actions]

This PR will trigger a minor release when merged.