Autoname unsaved buffer

[maekawatoshiki]

Summary

• Closes #13
• Adds a feature to save the text in an unsaved buffer to a file, which is named automatically based on its content.
  • Use the Markdown Copilot: Name and Save command.
  • The file path is formatted in which markdown.copilot.instructions.autonameFilepath specifies. Default: ${workspaceDir}/memo/${date}/${filename}.md

Optional tasks

• [x] Discuss details for this feature not mentioned on the issue
• [x] Allow more flexible formatting in file path (e.g., date format other than YYYY-MM-DD)

[maekawatoshiki]

Any updates on review?

[squld]

@maekawatoshiki I pushed a commit, so please review it.

• Process the path format using LLM, then it now works with date formats (yyyy-MM, etc.).
• Remove dependencies on fs and path.

[maekawatoshiki]

I've reviewed your changes and verified it works. LGTM.