Improving Lesson 1.3 by mentioning longest match while scanning tokens (

#3618)

Fixes #3539.

It makes more sense to me to add it to Lesson 1.3 instead of Lesson 1.4,
as we're introducing Parsing in this lesson. But I'm open to suggestions
to improve the text and where it should be! 😄

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Co-authored-by: rv-jenkins <[email protected]>

k-distribution/k-tutorial/1_basic/03_parsing/README.md

@@ -88,6 +88,13 @@ interprets terms according to the grammar defined by the developer. It is
 automatically converted into an AST of that term, and then the `colorOf`
 function is evaluated using the function rules provided in the definition.
 
+You can ask yourself: How does K match the strings between the double quotes?
+The answer is that K uses Flex to generate a scanner for the grammar. Flex looks
+for the longest possible match of a regular expression in the input. If there
+are ambiguities between 2 or more regular expressions, it will pick the one with
+the highest `prec` attribute. You can learn more about how Flex matching works
+[here](https://westes.github.io/flex/manual/Matching.html#Matching).
+
 Bringing us back to the file `lesson-03-a.k`, we can see that this grammar
 has given a simple BNF grammar for expressions over Booleans. We have defined
 constructors corresponding to the Boolean values true and false, and functions