Accessibility: Automatic chart description generation

[rokotyan]

Currently, the charts in Unovis, including network graphs and maps, lack some of the accessibility features to make them usable by all, including those with visual impairments or other disabilities.

To fill these gaps, we would like to implement an automatic accessibility description generation mechanism for all charts in Unovis. This feature should:

1. Automatically generate detailed textual descriptions of the charts' content.
2. Provide context-aware summaries for quick understanding.
3. Cover all chart types in Unovis, including but not limited to, bar charts, line charts, pie charts, scatter plots, network graphs, and maps.
4. Integrate with screen readers for a seamless user experience for visually impaired users.

Acceptance Criteria:

1. A visually impaired user should be able to understand the main content and details of the chart through the generated descriptions.
2. The generated description should change dynamically as the chart's data or configuration changes.
3. There should be an option for users to toggle the feature on/off according to their preference.
4. The feature should be tested across multiple screen readers to ensure compatibility.