Ordered list numbering

[Kristof-me]

Sometimes we start ordered lists from numbers different from 1 but this isn't supported.

Example:

Steps:

0. Check behind the door
1. Under the bed

The regex for it could be ^\s*\d\., but it's too complicated for the preprocessor as the parent element has to be modified to use:

<ol start="our_value">

This could be fixed with a post processor or explicit annotations (like 0. Check behind the door {class="zero-start"})
But right now we have no rules about this issue.