feat: Add version information to generated Markdown

[marcelosalloum]

Summary

Adds package version information to the generated markdown documentation. The version now appears near the top of the document, right after the introductory text and before the command overview/table of contents.

Changes

• Modified markdown generation to include version information when available
• Version is displayed as: **Version:** 1.2.3``
• Version display is conditional - only shown if the clap Command has a version set
• Updated all tests to reflect the new output format

Example Output

# Command-Line Help for `my-app`

This document contains the help content for the `my-app` command-line program.

**Version:** `1.2.3`

**Command Overview:**
(...)

Motivation

Having the version visible in the generated documentation helps users quickly identify which version of the tool the documentation corresponds to. Additionally, this aids AI agents that scrape documentation by providing clear version context.

[leighmcculloch]

Nice!