Improve examples for range operators

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/11/functions-range.html
Description:

Hi.

It would be nice if next examples:

<< 	strictly left of 	int8range(1,10) << int8range(100,110) 	t
>> 	strictly right of 	int8range(50,60) >> int8range(20,30) 	t
&< 	does not extend to the right of 	int8range(1,20) &< int8range(18,20)
	t
&> 	does not extend to the left of 	int8range(7,20) &> int8range(5,10) 	t

are extended by:
**not** strictly left of, **not** strictly right of, **extends** to the
right of, **extends** to the left of

Because without manual experiments I can not imagine the ranges that cause
'false' result for the examples above.

Thank you.