spec: add bar-horizontal specification

[github-actions]

New Specification: bar-horizontal

Related to #1946

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specification.md

bar-horizontal: Horizontal Bar Chart

Description

A horizontal bar chart displaying categorical data with rectangular bars extending horizontally from the y-axis. The length of each bar is proportional to the value it represents. This orientation is particularly effective when category names are long or numerous, as horizontal labels are easier to read than rotated vertical labels. Horizontal bar charts excel at rankings, comparisons, and survey results visualization.

Applications

• Displaying survey results with descriptive response options
• Showing ranked lists such as top products, countries by population, or employee performance
• Creating population pyramid base charts for demographic analysis

Data

• category (categorical) - Labels for each bar on the y-axis
• value (numeric) - Length of the bars representing the measured quantity
• Size: 5-20 categories recommended for readability
• Example: Survey response counts, country statistics, product performance metrics

Notes

• Bar heights should be consistent across all categories
• Consider sorting bars by value for easier comparison (largest to smallest or vice versa)
• Use a single color for all bars, or highlight specific bars to draw attention
• Ensure adequate spacing between bars for visual clarity
• Value labels can be placed at the end of bars or inside them

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Next: Add approved label to the issue to merge this PR.

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