Rendering option for rendering ordered list with constant whitespace

[edwar4rd]

When using comrak::format_commonmark,

1. something
2. something
3. something
...
10. something

gets format into

1.  something
2.  something
3.  something
...
10. something

with varying amount spaces, which isn't commonly seen in markdown and generates lint MD030 when checked with markdownlint.
Is it possible to add a option for this in the RenderOptions struct?

[edwar4rd]

See #465
I tried implementing this myself but wasn't too sure about the prefix part.