Add line numbers to Markdown code snippets

[walles]

With these changes

  37 
  38 	}
  39 
  40 	private static void untested() {
! 41 		System.out.println("This method has no tests");
! 42 	}
  43 
  44 }

Before

	}

	private static void untested() {
		System.out.println("This method has no tests");
	}

}

[walles]

Sorry about the test failures, will fix.

[walles]

Tests pass for me locally now.

[Bachmann1234]

Thanks for the PR, merging this in.

[Bachmann1234]

Released in https://pypi.org/project/diff-cover/9.0.0/

Thanks again!