Allow duplicate built-in reference types

According to [`ref`](https://perldoc.perl.org/functions/ref), Perl has the following built-in reference types:

- ARRAY
- CODE
- FORMAT
- GLOB
- HASH
- IO
- LVALUE
- REF
- REGEXP
- SCALAR
- VSTRING

As a developer, I encounter these literals fairly often in Perl code bases, and I would like to support allowing them multiple times, so I won't have to list them in each project (which means another duplicate in itself! :sweat_smile: )

I can shortly send a follow-up pull request about this, though I wonder about the best approach how to allow them:

- Should they be allowed unconditionally?
- Is it better to use a configuration option, like `allow_builtin_reference_types`?
- If using a configuration option, what's a good name for this?
- If using a configuration option to control this, should it be default on or off?