Replace audio element with video element in README

[jkmaina]

What

Brief description of the change.

Why

Link to the issue this addresses: Fixes #___

How

Summary of the approach taken.

PR Checklist

Quality Gates (all required)

• devenv shell fmt — code is formatted (Edition 2024)
• devenv shell clippy — zero warnings (-D warnings)
• devenv shell test — all non-ignored tests pass
• devenv shell check — fast workspace compilation check

Code Quality

• New code has tests (unit, integration, or property tests as appropriate)
• Public APIs have rustdoc comments with # Example sections
• No println!/eprintln! in library code (use tracing instead)
• No hardcoded secrets, API keys, or local paths

Hygiene

• No local development artifacts (.env, .DS_Store, IDE configs, build dirs)
• No unrelated changes mixed in (formatting, refactoring, other features)
• Branch naming follows convention (feat/, fix/, docs/, etc.)
• Commit messages follow conventional format (feat:, fix:, docs:, etc.)
• PR targets main branch

Documentation (if applicable)

• CHANGELOG.md updated for user-facing changes
• README updated if crate capabilities changed
• Examples added or updated for new features