[BUG] pkgsrc detection on macOS

### Read the FAQ first

- [x] I have checked the FAQ but the issue is not covered

### Description

I tried to install `fastfetch` from `pkgsrc` on macOS, but the package manager detection logic on macOS does not implemented the `pkgsrc` detection.
I actually tried to modify the source code by porting the `pkgsrc` detection logic on NetBSD (`src/detection/packages/packages_nbsd.c`) to macOS, and change the `pkgdb` path to match the common `/opt/pkg` bootstrap prefix on macOS, it does work.
I would like to request this issue being fixed, in order to provide `pkgsrc` detection out-of-box on macOS, without any manual modifications required.
Thank you.

### Version used

fastfetch 2.62.1-63 (aarch64)

### Bug prevalence

Always

### Regression

No

### Installation

Package manager

### Package manager

pkgsrc

### Screenshots

Following is a screenshot of `pkgsrc` detection working on macOS after manual source code modification.

### Configuration

```jsonc

```

### System information

```jsonc
not relevant
```

### Features built-in

```text
% fastfetch --list-features
threads
zlib
sqlite3
libzfs
```

Inizia leggendo src/detection/packages/packages_nbsd.c, quindi individua il percorso di rilevamento dei gestori di pacchetti macOS e confronta i gestori supportati con la logica pkgsrc segnalata. Verifica la modifica con un'installazione di pkgsrc su macOS che utilizzi il prefisso standard /opt/pkg e conferma che fastfetch rilevi pkgsrc senza modifiche manuali al codice sorgente.

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