Add rscep extension for rubocop

A magyar leírás lent található

## English description

We should use the [rubocop-rscpec](https://github.com/rubocop-hq/rubocop-rspec) gem to standardize the format of the specs.

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## Magyar leírás

Jó lene a rubocop-rspec-et hozáadni a projekthez, hogy egységes formátuma legyene a teszteknek.

No files or tests are named in the issue. Start by locating the project's RuboCop configuration and test setup, then determine where the rubocop-rspec gem and extension should be added; done means the extension is enabled and the specs follow its checks.

Written by the indexing model from the issue text.