Enhancement: Display README files in Description.

[mcmonkey4eva]

The registry should load, store, and process README.md files - ie the full markdown built details.

When for example loading the page https://www.comfyregistry.org/nodes/sd-dynamic-thresholding [instead of / in addition to] showing the description text entered directly into the toml, it should render the markdown contents of the README file.

This would also be available eg for in the future if a Search function is added, readmes would be searched, or if Manager swaps to use Registry as its backend, it would be able to render the remote readme for nodes not-yet-downloaded directly in-UI.