Category Labels (RFC)

Needs comments / suggestions on how to handle regex labels for commitlog.

Currently the categorization works in the following way.

Eg: a catg regex like so would produce the labels
```sh
$ commitlog g --categories="feat:,fix:"
```

```md
## feat:
## fix:
```

Though this doesn't make sense when you have really complex regex's handling the categorisation.

So, there needs to be a way to create labels for these category regexes

One possible way is to change the way the flags are parsed and have more than one instance of the flag.
```sh
$ commitlog --category="Features%%feat:" --category="Fixes%%fix:"
```

Considering the chances of `%%` being together in a regex being very rare and also since the logic would only take the first separation to get the `LABEL` everything else would be compiled back as regex.

Inizia esaminando il parsing attuale delle categorie alla base dell’opzione --categories e confrontalo con la forma ripetuta --category proposta. Definisci come separare le label dalle espressioni regolari complesse, quindi verifica che le intestazioni delle categorie vengano generate con le label richieste sia per i pattern semplici sia per quelli complessi.

Scritto dal modello di indicizzazione a partire dal testo della issue.