add: Makefile for dev env

Makefile

+# makefile used for testing
+#
+#
+all: install test
+
+install:
+	python3 -m pip install -e .[test]
+
+test:
+	python3 -m pytest -vv \
+	    --cov=$(PWD)/src/rechunk_data --cov-report=html:coverage_report \
+	    --junitxml report.xml --cov-report xml \
+		$(PWD)/src/rechunk_data/tests
+	python3 -m coverage report
+
+lint:
+	mypy --install-types --non-interactive
+	black --check -t py310 -l 79 src
+	flake8 src/rechunk_data --count --max-complexity=15 --max-line-length=88 --statistics --doctests
\ No newline at end of file

setup.py

 #!/usr/bin/env python3
-"""Setup script for packaging checkin."""
+"""Setup script for packaging check-in."""
 
 import json
 from pathlib import Path
@@ -51,9 +51,10 @@ setup(
             "pytest-cov",
             "testpath",
             "types-mock",
+            "flake8",
         ],
     },
-    python_requires=">=3.6",
+    python_requires=">=3.9",
     classifiers=[
         "Development Status :: 3 - Alpha",
         "Environment :: Console",