[cached-path-relative] Add documentation to new definition

Author: TeamworkGuy2

types/cached-path-relative/index.d.ts

@@ -3,6 +3,11 @@
 // Definitions by: TeamworkGuy2 <https://github.com/TeamworkGuy2>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
+/**
+ * Memoize the results of the path.relative function. path.relative can be an expensive operation
+ * if it happens a lot, and its results shouldn't change for the same arguments.
+ * Use it just like your normal path.relative, but it's memoized.
+ */
 declare function cachedPathRelative(from: string, to: string): string;
 
 export = cachedPathRelative;