add dev group containing just pytest for convenience

Author: niklasmohrin

pyproject.toml

@@ -13,6 +13,11 @@ dependencies = [
 ]
 requires-python = ">=3.10"
 
+[project.optional-dependencies]
+dev = [
+    "pytest",
+]
+
 [project.scripts]
 bt = "bapctools.cli:main"