Bench mark to load page per user

Would be nice to know how long it take to a user to fully load a page.
this could help to find , page that are to long to load , or if loading time make people go away or click an other page.
also , it can help to improve code for some special browser , when it take to long to load for what ever reason it can be.


see Propose Page speed reports, Load time analytics · Issue #1700 · matomo-org/matomo · GitHub