Changes to introductory text. (rust-unofficial#299)

* change to introductory text on design patterns with a very brief description

* minor textual adjustments

* shortened line length

* markdown fixes

* Update intro.md

removed redundancy

Co-authored-by: Marco Ieni <[email protected]>

Co-authored-by: Marco Ieni <[email protected]>

intro.md

@@ -7,10 +7,17 @@ If you are interested in contributing to this book, check out the
 
 ## Design patterns
 
-When developing programs, we have to solve many problems.
-A program can be viewed as a solution to a problem.
-It can also be viewed as a collection of solutions to many problems.
-All of these solutions work together to solve a bigger problem.
+In software development, we often come across problems that share
+similarities regardless of the environment they appear in. Although the
+implementation details are crucial to solve the task at hand, we may
+abstract from these particularities to find the common practices that
+are generically applicable.
+
+Design patterns are a collection of reusable and tested solutions to
+recurring problems in engineering. They make our software more modular,
+maintainable, and extensible. Moreover, these patterns provide a common
+language for developers to use, making them an excellent tool for effective
+communication when problem-solving in teams.
 
 ## Design patterns in Rust