Support Github Issue creation by title and a folder of documents

[qdriven]

Task 4: Support Github Issue creation by title and a folder of documents

1. Support create issue with a folder of docs
2. Every single document is an issue content
3. The issue title is the document name or the Headline of document, headline of the document is the default option if it is a markdown file
4. The issue body is the document content

[qdriven]

Implementation Complete

• Added spark git batch-issue <repo> -d <docs> command
• Title extracted from first # heading in each markdown file, falls back to filename
• Supports --dry-run, --label flags
• 8 unit tests passing
• Commit: bbc406b