V18 change on EXPLAIN ANALYZE

Robert Hass committed ddb17e387aa28d61521227377b00f997756b8a27,
which changed how EXPLAIN indicates fractional rows. That's cool but I have
to see that change on sources because it's not explained on DOCs.

One can understand that cost=4.36, that actual time=0.009, but what means
rows=10.43 ? Costs and Time having decimals are fine but what is a row and
a half ?

So, I don't know exactly how to explain this change but I think it would be
good to have a new paragraph on [1] and explain that now when nloops > 1,
we now display two digits after the decimal point, rather than none.

[1] -
https://www.postgresql.org/docs/current/using-explain.html#USING-EXPLAIN-ANALYZE

regards
Marcos