Support for measuring Interaction to Next Paint (INP)

[pierres]

Description

In order to be able to track the new web vital metric Interaction to Next Paint (INP), it would be great if it could be measured and made available as variable substitution similar to e.g. ${cumulativeLayoutShift}.

Alternatives Considered

We currently use <amp-analytics> on pages meant for Google's AMP cache, as well on their canonical counterparts. This also means custom code that e.g. uses the web-vitals library cannot be utilized.

Additional Context

No response

[erwinmombay]

Fixed by #39345 , it is currently under an experiment guard as we need to confirm the data we are transmitting