spec: add bar-race-animated specification

[github-actions]

New Specification: bar-race-animated

Related to #3653

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specification.md

bar-race-animated: Animated Bar Chart Race

Description

An animated horizontal bar chart that visualizes how rankings and values change over time. Bars smoothly transition positions as their values update, with the chart reordering to maintain a sorted ranking at each time step. This dynamic visualization format is highly engaging for storytelling with time-series data, making it popular for showing the rise and fall of entities like countries, companies, or products over extended periods.

Applications

• Visualizing how country GDP rankings have shifted over decades, with bars racing as economies grow and overtake one another
• Tracking brand market share evolution throughout the year, showing competitive dynamics in an engaging animated format
• Displaying historical sports team standings or player statistics over multiple seasons, revealing dynasty periods and surprising reversals

Data

• entity (categorical) - The items being compared and ranked (countries, companies, teams, products)
• time (datetime or numeric) - Time points for each snapshot, driving the animation sequence
• value (numeric) - The metric determining bar length and ranking at each time point
• color (categorical, optional) - Category or group for coloring bars consistently
• Size: 10-20 entities with 20-100 time points recommended for smooth, comprehensible animation
• Example: Country GDP by year, streaming platform subscribers by month, brand revenue by quarter

Notes

• Bars should be sorted by value at each frame, with smooth transitions for position changes
• Entity labels should remain attached to their bars throughout the animation
• A visible time indicator (counter, axis label, or title) should update during playback
• Animation speed should be configurable or use a reasonable default duration
• For static output or libraries without animation support, show a small multiples grid of key time snapshots
• Consider including play/pause controls and a timeline scrubber for interactive versions
• Color should remain consistent for each entity across all frames for tracking

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

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