editorconfig: add max_line_length for Python files

[sumnerevans]

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

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Pull request includes a sign off
• Code style is correct
  (run the linters)

[DMRobertson]

Good idea!