feat(images): add support for image previewing with Snacks

[kristijanhusak]

Summary

Add support for rendering images using snacks.image

Related Issues

Related: folke/snacks.nvim#1276

Changes

• Add images.scm that is read by Snacks to render images
• Add custom directive that sets metadata for the node to render the image

Checklist

I confirm that I have:

• Followed the
  Conventional Commits
  specification (e.g., feat: add new feature, fix: correct bug,
  docs: update documentation).
• My PR title also follows the conventional commits specification.
• Updated relevant documentation, if necessary.
• Thoroughly tested my changes.
• Added tests (if applicable) and verified existing tests pass with
  make test.
• Checked for breaking changes and documented them, if any.