update dotnet application

[commjoen]

What kind of changes does this PR include?

• Fixes or refactors in the spoil of dotnet
• A new challenge
• Additional documentation
• Something else

Description

Relations

References

Checklist:

• All the contributions made are solely the work of me and my co-authors
• I tested the changes in this PR (if applicable)
• I added unit tests to ensure my change works (when change in Java or on front-end code)
• Quickbuild.sh is extended to compile the binary for all target environnments
• Github actions are implemented to publish the new challenge
• A spoil command is implemented to return the actual answer
• The correct and incorrect answer strings are compliant with Contributing.md.
• The PR passes pre-commit hooks and automated tests