Feature Request: Markdown Formatter

[snapsynapse]

First off, thank you for maintaining this library! The clean formatter architecture makes it really easy to work with transcripts programmatically.

I'm interested in contributing a MarkdownFormatter to sit alongside the existing SRT/WebVTT/JSON formatters. My use case is generating readable documentation from my own video content, where the current text formatter works but lacks structure (headings, paragraph breaks, metadata blocks).

I'm thinking something like:

---
source: "https://youtube.com/watch?v=..."
title: "Video Title"
channel: "https://www.youtube.com/@..."
---

[paragraph of grouped sentences]

[paragraph of grouped sentences]

Before I start, wanted to check if this aligns with the project's scope and if you have any preferences on the implementation approach? Thanks.