difference-of-squares: Updated the README
Relevant PR:
@@ -12,6 +12,10 @@ Hence the difference between the square of the sum of the first
ten natural numbers and the sum of the squares of the first ten
natural numbers is 3025 - 385 = 2640.
+You are not expected to discover an efficient solution to this yourself from
+first principles; research is allowed, indeed, encouraged. Finding the best
+algorithm for the problem is a key skill in software engineering.
+
## Rust Installation
Refer to the [exercism help page][help-page] for Rust installation and learning
