Small changes and bug fixes:
- [Build] Implement #175: build artifacts are now automatically uploaded to the GitHub release.
- [Build] Implement #201: allow using a version of doctest already installed on the system (used for testing snitch).
- [Build] The license file
LICENSEis now installed by CMake indoc/snitch/LICENSE, and also uses this location in the release packages (instead of the root of the zip).