Fix TSC generating broken .d.ts files

lib/index.js

@@ -119,7 +119,7 @@
  * @property {VFileReporter | string | undefined} [reporter]
  *   Reporter to use (default: `'vfile-reporter'`); if a `string` is passed,
  *   it’s loaded from `cwd`, and `'vfile-reporter-'` can be omitted
- * @property {VFileReporterKnownFields & {[key: string]: unknown} | undefined} [reporterOptions]
+ * @property {VFileReporterOptions | undefined} [reporterOptions]
  *   Config to pass to the used reporter (optional).
  * @property {UnifiedSettings | undefined} [settings]
  *   Configuration for the parser and compiler of the processor (optional).
@@ -190,10 +190,15 @@
  *   for unknown fields in options and async support.
  * @param {Array<VFile>} files
  *   Files.
- * @param {VFileReporterKnownFields & {[key: string]: unknown}} options
+ * @param {VFileReporterOptions} options
  *   Configuration.
  * @returns {Promise<string> | string}
  *   Report.
+ *
+ * @typedef {{[Key in keyof VFileReporterKnownFields]: VFileReporterKnownFields[Key]} & Record<string, unknown>} VFileReporterOptions
+ *   Configuration.
+ *
+ *   Note: this weird type fixes TSC:
  */
 
 import process from 'node:process'