Rename workflow and fix CI badge

Author: MakisH

.github/workflows/markdownlint.yml .github/workflows/pre-commit.yml.github/workflows/markdownlint.yml renamed to .github/workflows/pre-commit.yml

@@ -1,6 +1,6 @@
 # Simulation Software Engineering Lecture Material
 
-![markdownlint](https://github.com/Simulation-Software-Engineering/lecture-materials/actions/workflows/markdownlint.yml/badge.svg)
+![pre-commit](https://github.com/Simulation-Software-Engineering/lecture-materials/actions/workflows/pre-commit.yml/badge.svg)
 [![PDFs](https://github.com/Simulation-Software-Engineering/lecture-materials/actions/workflows/create-pdfs-from-markdown.yml/badge.svg)](https://github.com/Simulation-Software-Engineering/Lecture-Material/actions/workflows/create-pdfs-from-markdown.yml)
 [![CC BY 4.0][cc-by-shield]][cc-by]