docs: add reporter setting to settings reference

[nozomiishii]

Summary

The reporter option is documented as a CLI flag (--reporter) on the install page, and it works correctly when set in either .npmrc or pnpm-workspace.yaml. However, it was missing from the settings reference page.

This omission causes practical issues for users who want to configure reporter at the project level:

• Setting reporter=append-only in .npmrc triggers an npm warning:

  npm warn Unknown user config "reporter". This will stop working in the next major version of npm. See `npm help npmrc` for supported config options.
  

• Setting reporter: append-only in pnpm-workspace.yaml triggers an editor/IDE warning from SchemaStore validation:

  Property reporter is not allowed. yaml-schema: pnpm Workspace (pnpm-workspace.yaml)(513)
  

Both configurations work as expected with pnpm, but users have no warning-free way to set this option.

Changes

Added reporter setting documentation between loglevel and useBetaCli in docs/settings.md, following the same format as other enum-type settings like color and loglevel.

Related

• Closes Add reporter config setting to npmrc pnpm#7238
• https://pnpm.io/cli/install#--reportername

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[nozomiishii]

I've also submitted a PR to add reporter to the SchemaStore schema for pnpm-workspace.yaml: SchemaStore/schemastore#5512