[FEATURE] Enable configurable custom and default text roles

[linawolf]

See https://docutils.sourceforge.io/docs/ref/rst/directives.html#role

[jaapio]

I could not find this in your changes to that's why I ask it, default text roles set by a document are document bases, aren't they? Otherwise the order of parsing matters and I don't thing we have that order currently. It would also disallow caching of the full documents between runs as the parser would be in a different state. Therefor I think it would make sense to add these textroles somehow in the DocumentParserContext?

Same applies for document defined or replaced roles, those should only apply to the current document from the point where the role was defined.

[linawolf]

We usually define textroles in the includes.rst.txt which is included at the beginning of each document. So I supose it is probably defined on document level. will have a look at it

[linawolf]

@jaapio Each DocumentParserContext now manages a clone of the TextRoleFactory such that changes made to it by one directive do not apply to another document. Also added a test for this.

[jaapio]

Thanks this looks good!