Add animated bar chart template

[michaeljamesknight]

Why

The existing Bar Chart example was a single exported animation, so it could not advance through chart points as discrete OGraf steps or expose the visual assets as editable graphic data.

What changed

• Replaced the bundled runtime with a lightweight DOM/CSS OGraf component that reveals one bar per playAction step across six steps.
• Declared the chart points and background image input in bar-chart.ograf.json, including step-specific action durations.
• Added the bundled SVG background asset and updated the example documentation.

Notes

The referenced Figma file redirected to login during implementation, so the existing repository thumbnail was used as the visual reference. The site validator could not run because the local html-validate dependency is not installed; module syntax, manifest JSON, step/asset declarations, and diff whitespace were validated successfully.