Enrich the developer API reporting documentation by adding a description of the format_metrics parameter

[Chardonneaur]

Hi Team,

The format_metrics can turn percent rate into numerical values which is really important for end users using data visualization software.
Documenting this parameter would be very helpful on: https://developer.matomo.org/api-reference/reporting-api
Here is the problem that this parameter is solving: https://youtu.be/DrXyqUC64ic
Thank you,