feat(highcharts): implement contour-basic (#5335)

## Implementation: `contour-basic` - python/highcharts

Implements the **python/highcharts** version of `contour-basic`.

**File:** `plots/contour-basic/implementations/python/highcharts.py`

**Parent Issue:** #855

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:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/24867714420)*

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