[FEATURE] Local conversion between formats

[nomailme]

Hi! Thanks for the awesome tool.

Describe the solution you'd like
It would be awesome if there was a command that allows conversion from one content format into the other one. Without connection to the actual Confluence server.

Currently, I use md2conf tool for local conversion. But it seems that the tools are similar and if I can have only one tool that would be easier to maintain.

Use case
I have a workflow, that is uploading markdown file to the coroporate confluence server:

1. Clean working directory
2. Build related artifacts that are used by this markdown page (images, related pages, etc.)
3. Copy files from project directory to the working directory
4. Download page from Confluence (storage format), extract medata, comments, etc.
5. Convert markdown file to Confluence CSF format. Extract macros and comments
6. Merge macros and comments to the converted page
7. Upload to Confluece
8. Call it a day 🥇

Example usage

confluence-cli convert --input-file document.md --input-format markdown --output-file document.csf --output-format storage

Again, thank you for this tool