feat(pygal): implement spectrogram-basic (#3144)

## Implementation: `spectrogram-basic` - pygal

Implements the **pygal** version of `spectrogram-basic`.

**File:** `plots/spectrogram-basic/implementations/pygal.py`

**Parent Issue:** #2927

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:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20627534676)*

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