Address new TypeScript warnings in core files, improve type definitions.

lib/cache.mjs

@@ -6,6 +6,7 @@ import { filterByTypes } from "../helpers/micromark-helpers.cjs";
 /** @typedef {import("markdownlint").RuleParams} RuleParams */
 /** @typedef {import("markdownlint").MicromarkToken} MicromarkToken */
 /** @typedef {import("markdownlint").MicromarkTokenType} MicromarkTokenType */
+/** @typedef {import("../helpers/helpers.cjs").GetReferenceLinkImageDataResult} GetReferenceLinkImageDataResult */
 
 /** @type {Map<string, object>} */
 const map = new Map();
@@ -68,9 +69,10 @@ export function filterByTypesCached(types, htmlFlow) {
 /**
  * Gets a reference link and image data object.
  *
- * @returns {Object} Reference link and image data object.
+ * @returns {GetReferenceLinkImageDataResult} Reference link and image data object.
  */
 export function getReferenceLinkImageData() {
+  // @ts-ignore
   return getCached(
     getReferenceLinkImageData.name,
     () => helpersGetReferenceLinkImageData(micromarkTokens())