fix: change setup-cfg keys from dash to snake case

Setuptools no longer accepts options containing uppercase or dash characters in
setup.cfg

Signed-off-by: Dominic Evans <[email protected]>

Author: dnwe

setup.cfg

@@ -1,11 +1,11 @@
 [metadata]
-description-file = README.md
+description_file = README.md
 
 [wheel]
 universal = True
 
 [flake8]
-max-line-length = 100
+max_line_length = 100
 
 [tool:pytest]
 norecursedirs=tests/testing