Add single file esbuild target for building openneuro-cli

[nellh]

Is your feature request related to a problem? Please describe. It's pretty easy as a developer or user installing the CLI to end up with either a build broken by dependency contamination or other local state. The build steps are meant to maintain CommonJS support but we really could sidestep that issue by directly bundling one output file with esbuild for NodeJS instead.

Describe the solution you'd like Build for the CLI should output one file that can be executed without npm or yarn.

Describe alternatives you've considered Port everything to Deno :eyes:

Additional context This was tripping up some testing in #2715