add tox env to update all dev dependencies

tox.ini

@@ -33,3 +33,17 @@ commands = mypy
 [testenv:docs]
 deps = -r requirements/docs.txt
 commands = sphinx-build -W -b dirhtml docs docs/_build/dirhtml
+
+[testenv:update-requirements]
+deps =
+    pip-tools
+    pre-commit
+skip_install = true
+change_dir = requirements
+commands =
+    pre-commit autoupdate -j4
+    pip-compile -U build.in
+    pip-compile -U docs.in
+    pip-compile -U tests.in
+    pip-compile -U typing.in
+    pip-compile -U dev.in