general/drills: Add "FaaS service" written task as exam

[vladiouz]

edited config.yaml and faas-service.md

Prerequisite Checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Updated relevant documentation (if needed).

Description of changes

[github-actions]

Published at https://cs-pub-ro.github.io/operating-systems/57/

[teodutu]

The PR is OK. Good job!

Now update your commit description to be less vague. Follow the example from this commit [1] and use imperative verbs, not the past tense of the indicative mood.

Second, when you create a PR, you've already seen a template description pop up. Move the description of your changes under the Description of changes heading.

[1] 9c113e8