feat: duplicate tag names should throw error

[joriverm]

Is your feature request related to a problem? Please describe.
a openapi spec file that has 2 tags with the same name doesn't raise an error nor warning about it.

Describe the solution you'd like
i would expect the tool to at least throw a warning about the tag being duplicate. the swagger editor ( https://editor.swagger.io/ ) does complain about it and considers it an error

Describe alternatives you've considered
N/A, we currently have the tool running on a cron and we will see when it is added :)

Additional context
used json to test : petstore.json
used command : redocly lint petstore.json --lint-config=error --format=json
current log : log.txt

[tatomyr]

This isn't a bug, but rather a feature request. We need to add a rule to check for the uniqueness of tag names. Anyway, thanks for creating the issue!

[joriverm]

my mistake, i considered it a bug as it is apparently in the specs, but fair enough!
if any testing or info is needed let me know!