editorconfig: add max_line_length for Python files (#13228)

See the documentation for the property here:
https://github.com/editorconfig/editorconfig/wiki/EditorConfig-Properties#max_line_length

Signed-off-by: Sumner Evans <me@sumnerevans.com>

.editorconfig

@@ -7,3 +7,4 @@ root = true
 [*.py]
 indent_style = space
 indent_size = 4
+max_line_length = 88

changelog.d/13228.misc

@@ -0,0 +1 @@
+Add `max_line_length` setting for Python files to the `.editorconfig`. Contributed by @sumnerevans @ Beeper.