feat: add --from-jsr-config option

[marvinhagemeister]

Based on a feature request on discord:

This option is useful for testing Deno-first JSR packages in Node. Passing this flag installs all jsr:* and npm:* packages defined in the "imports" field as npm package which effectively adds it to package.json.

Input:

// jsr.json or deno.json (or their *.jsonc variants)
{
  "imports": {
    "@std/encoding": "jsr:@std/encoding@^0.216.0"
    "preact": "npm:[email protected]"
  }
}

Run: npx jsr i --from-jsr-config

Result:

// package.json
{
  "dependencies": {
    "@std/encoding": "npm:@jsr/std__encoding@^0.216.0",
    "preact": "10.20.0"
  }
}

[lucacasonato]

imports is not valid in jsr.json, only in deno.json. The CLI allows this for deno publish right now (that's a bug), but not other subcommands. We should thus not detect imports in jsr.json.