Update loader.js once Broadstreet Ads update it

Problem/Motivation

On 2024-03-22 I emailed Broadstreet to let them know that their sample loader code fails against eslint. They said

Proposed resolution

Wait for Broadstreet to update their example v2 loader code.
Update loader.js.

Remaining tasks

Update loader.js.

User interface changes

The loader.js passes the eslint test.

API changes

n/a

Data model changes

n/a