improve forkJoin exercises

projects/combining-streams/src/lib/exercises/forkJoin/docs/forkJoin.solution.md

 # Combining HTTP requests - Solution
 
-## Combining Http Calls
-
-We managed to combine two http calls with the `forkJoin` operator into a single list of `BlogPost`.
+## Implementation
 
 **Component**
 ```Typescript
@@ -29,3 +27,8 @@ export class SolutionForkJoinComponent {
 
 }
 ```
+
+## Conclusion
+
+Great! We managed to combine two http calls with the `forkJoin` operator into a single list of `BlogPost`. But what if we want to
+handle data manipulations? In a next step we refactor our architecture to a minimal http caching solution.