Deno 2.0 support

[kuchta]

Deno 2.0 supports managing dependencies in package.json, but using ncu with -p deno fails when it doesn't find deno.json with a confusing error

No package.json

Please add a package.json to the current directory, specify the --packageFile or --packageData options, or pipe a package.json to stdin and specify --stdin.

It should probably fallback to using package.json.