docs(courses): improve text for courses section (#179)

COURSES.md

@@ -1,14 +1,21 @@
-## Courses
+## Courses on Website Performance Optimization (WPO)
 
-> Best Courses about WPO
+If you want to master the art of Website Performance Optimization (WPO), check out these courses from reputable platforms:
 
-- [[Pluralsight] Website Performance](https://www.pluralsight.com/courses/website-performance)
-- [[Pluralsight] Web Performance](https://www.pluralsight.com/courses/web-performance)
-- [[Pluralsight] Using Google PageSpeed Insights](https://www.pluralsight.com/courses/google-pagespeed-insights-web-performance)
-- [[Pluralsight] A Web Developer's Guide to Images](https://www.pluralsight.com/courses/dev-guide-to-images)
-- [[Pluralsight] Responsive Web Images](https://www.pluralsight.com/courses/responsive-web-images)
-- [[Pluralsight] Tracking Real World Web Performance](https://www.pluralsight.com/courses/web-performance-tracking)
-- [[LinkedIn Learning] Designing Websites for Performance](https://www.linkedin.com/learning/designing-websites-for-performance)
-- [[LinkedIn Learning] HTTP/2: Developing for Performance](https://www.linkedin.com/learning/http-2-developing-for-performance)
-- [[Channel9] Web Performance](https://channel9.msdn.com/Shows/Web-Hack-Wednesday/Web-Performance/)
+### [Pluralsight]
 
+1. [Website Performance](https://www.pluralsight.com/courses/website-performance)
+2. [Web Performance](https://www.pluralsight.com/courses/web-performance)
+3. [Using Google PageSpeed Insights](https://www.pluralsight.com/courses/google-pagespeed-insights-web-performance)
+4. [A Web Developer's Guide to Images](https://www.pluralsight.com/courses/dev-guide-to-images)
+5. [Responsive Web Images](https://www.pluralsight.com/courses/responsive-web-images)
+6. [Tracking Real World Web Performance](https://www.pluralsight.com/courses/web-performance-tracking)
+
+### [LinkedIn Learning]
+
+1. [Designing Websites for Performance](https://www.linkedin.com/learning/designing-websites-for-performance)
+2. [HTTP/2: Developing for Performance](https://www.linkedin.com/learning/http-2-developing-for-performance)
+
+These courses cover a range of essential topics to optimize your website's performance. Whether you're interested in speed optimization, image handling, or monitoring real-world web performance, these courses have got you covered. Happy learning!
+
+Note: This listing has no affiliation with the companies and teachers of the courses.