openneuro CLI support for Node 18+

[nellh]

Describe the bug Due to differences in the NodeJS native fetch implementation and the polyfill we've been using, many operations do not work correctly with Node 18. We recommend Node 16 but 16 is about to move to security only releases.

To Reproduce Steps to reproduce the behavior:

1. Install Node 18
2. npm install @openneuro/cli
3. Attempt to download or upload anything.

Expected behavior A clear and concise description of what you expected to happen.

Additional context

A workaround that gets things mostly functional is to run with --no-experimental-fetch. If you've installed the CLI in a local directory, it can be run like so:

node --no-experimental-fetch ./node_modules/.bin/openneuro ...