Fixed an error in the 'An incomparable undefined' section. The value 'undefined' is not only equal to 'null', but to 'undefined' as well.

Author: Azaldin Freidoon

1-js/02-first-steps/08-comparison/article.md

@@ -193,7 +193,7 @@ Why does it dislike zero so much? Always false!
 We get these results because:
 
 - Comparisons `(1)` and `(2)` return `false` because `undefined` gets converted to `NaN` and `NaN` is a special numeric value which returns `false` for all comparisons.
-- The equality check `(3)` returns `false` because `undefined` only equals `null` and no other value.
+- The equality check `(3)` returns `false` because `undefined` only equals `null`, `undefined`, and no other value.
 
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