docs(pipes): add information and statement titles (2)

Author: svenson95

docs/src/content/docs/challenges/angular/8-pipe-pure.md

@@ -9,6 +9,8 @@ sidebar:
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+## Information
+
 This is the first of three `@Pipe()` challenges, the goal of this series is to master **pipes** in Angular.
 
 Pipes are a very powerful way to transform data in your template. The difference between calling a function and a pipe is that pure pipes are memoized. So they won't be recalculated every change detection cycle if their inputs haven't changed.