add tox.ini with envs lint, format, run-notebooks

tox.ini

@@ -0,0 +1,33 @@
+[tox]
+lint_folders =
+    "{toxinidir}/notebooks"
+
+[testenv]
+
+[testenv:run-notebooks]
+deps =
+    numpy
+    scipy
+    matplotlib
+    ipywidgets
+    jupyter
+commands =
+    jupyter execute {toxinidir}/notebooks/01-BasisExpansion.ipynb
+
+[testenv:format]
+# formats project source code files
+skip_install = true
+deps =
+    black[jupyter]
+commands =
+    black {[tox]lint_folders}
+
+[testenv:lint]
+skip_install = true
+deps =
+    flake8-nb
+commands =
+    flake8_nb {[tox]lint_folders}
+
+[flake8_nb]
+max_line_length = 88