pyproject: Add build-system

Author: tony

pyproject.toml

@@ -78,3 +78,7 @@ test = ["pytest", "pytest-rerunfailures"]
 coverage = ["codecov", "coverage", "pytest-cov"]
 format = ["black", "isort"]
 lint = ["flake8"]
+
+[build-system]
+requires = ["poetry_core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"