Add a conclusion page

Write a conclusion page about what we have learned in this course.

General features that we can find in all languages:

• Git
• Static code checking & linting:
  • type checking (mypy)
  • code errors (ruff)
  • code improvements (ruff)
• Test framework (pytest)
• Test coverage (cov)
• Containers (arrays, maps, sets, ...)
• ...