Add missing counterexamples to the documentation

[toniedzwiedz]

While going over the Wiki and the markdown files, I ran into a few files that look like they're supposed to show examples and counterexamples of valid/invalid code.

Examples:

• https://github.com/Cognifide/AEM-Rules-for-SonarQube/blob/master/src/main/resources/rules/HTL-11.md
• https://github.com/Cognifide/AEM-Rules-for-SonarQube/blob/master/src/main/resources/rules/AEM-15.md

Please confirm:

1. If they're used
2. How they're used

And complete them