Replace node-fetch with native Node fetch implementation

[atwupack]

There is a native fetch implementation which could be used instead of node-fetch.

• node-fetch has not been updated in over two years and most of its features are not used.
• It has to be checked what the minimal stable version of Node includes the implementation.
• As the new major version of commander requires Node 20 it would be ok to upgrade to at least that version of Node (Drop support for Node 18 and 23 #28)

[atwupack]

The libraries node-fetch and nodejs-file-downloader have been replaced with undici which is the official fetch implementation for Node.