docs: add details in CONTRIBUTING.md

[EuphoricThinking]

Add black installation details in CONTRIBUTING.md
as in README.md

Description

Added information about black installation in CONTRIBUTING.md, as it is in README.md. A possible contributor (who could focus on CONTRIBUTING.md) might have problems with formatting, since targets format-apply and format-check are not built if black is not installed (issue based on a true story).

Checklist

• Code compiles without errors locally
• All tests pass locally
• CI workflows execute properly

• CI workflows, not executed per PR (e.g. Nightly), execute properly
• New tests added, especially if they will fail without my changes
• Added/extended example(s) to cover this functionality
• Extended the README/documentation
• All newly added source files have a license
• All newly added source files are referenced in CMake files
• Logger (with debug/info/... messages) is used