[Bug]: Roles cannot be checked as they are not defined

[brotkrueml]

Summary

Roles, like

:sql:`SELECT * FROM table`

are not defined, so typos or unsupported roles cannot be warned about, like (mind the g instead the q):

:sgl:`SELECT * FROM table`

In Sphinx, custom roles have to be defined:
https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#inline-code-highlighting

On rendering, Sphinx displays an error about an unknown role:

 ERROR: Unknown interpreted text role "sgl".

This way, the user can spot the error and correct it.

Guides holds no definition of custom roles and therefore cannot warn about it.

[jaapio]

@linawolf it looks like the \phpDocumentor\Guides\RestructuredText\TextRoles\DefaultTextRoleFactory we do collect the roles that are known by the parser. I think we can use trigger a warning when we fall back to the generic role. But that seems not always valid to me as you can set the default role via a directive. Which makes this expected behavior. On the other hand it would be nice if we could detect typo's what do you think?