Update docstring for helper fun toArrayBuffer

Author: peterMuriuki

setupTests.js

@@ -52,6 +52,9 @@ Object.defineProperty(window, 'location', {
   writable: true,
 });
 
+/** Converts an object's binary to an arrayBuffer, useful when we
+ * later want to convert it to a base 64 ascii string
+ */
 function toArrayBuffer(buffer) {
   const arrayBuffer = new ArrayBuffer(buffer.length);
   const view = new Uint8Array(arrayBuffer);