doc: Add example for NaN comparison (JuliaLang#38953)

doc/src/manual/integers-and-floating-point-numbers.md

@@ -369,6 +369,7 @@ the real number line:
 | `-Inf16`  | `-Inf32`  | `-Inf`    | negative infinity | a value less than all finite floating-point values              |
 | `NaN16`   | `NaN32`   | `NaN`     | not a number      | a value not `==` to any floating-point value (including itself) |
 
+
 For further discussion of how these non-finite floating-point values are ordered with respect
 to each other and other floats, see [Numeric Comparisons](@ref). By the [IEEE 754 standard](https://en.wikipedia.org/wiki/IEEE_754-2008),
 these floating-point values are the results of certain arithmetic operations:
@@ -409,6 +410,18 @@ NaN
 
 julia> 0 * Inf
 NaN
+
+julia> NaN == NaN
+false
+
+julia> NaN != NaN
+true
+
+julia> NaN < NaN
+false
+
+julia> NaN > NaN
+false
 ```
 
 The [`typemin`](@ref) and [`typemax`](@ref) functions also apply to floating-point types: