Feature request: expose image download/export support in the CLI

Hi! Thanks for building and maintaining this project.

As far as I can tell, the MCP server already supports downloading images/assets during tool usage, and the CLI also supports the fetch subcommand for retrieving design data directly.

Would you consider exposing the existing image download/export behavior through the CLI as well?

For example, something like:

figma-developer-mcp download-images \
  --file-key <fileKey> \
  --node-id <nodeId> \
  --format png
  --scale 2
  --image-dir ./exports