[types] add a helpful hover description

Author: ljharb

index.d.ts

@@ -1,3 +1,9 @@
+/**
+ * Determines the type of the given collection, or returns false.
+ *
+ * @param {unknown} value The potential collection
+ * @returns {TypedArrayName | false | null} 'Int8Array' | 'Uint8Array' | 'Uint8ClampedArray' | 'Int16Array' | 'Uint16Array' | 'Int32Array' | 'Uint32Array' | 'Float32Array' | 'Float64Array' | 'BigInt64Array' | 'BigUint64Array' | false | null
+ */
 declare function whichTypedArray(value: Int8Array): 'Int8Array';
 declare function whichTypedArray(value: Uint8Array): 'Uint8Array';
 declare function whichTypedArray(value: Uint8ClampedArray): 'Uint8ClampedArray';
@@ -52,4 +58,4 @@ declare namespace whichTypedArray {
     | BigUint64ArrayConstructor;
 }
 
-export = whichTypedArray;
+export = whichTypedArray;