Add lit-html as an example of an importable module

[prantlf]

No description provided.

[wkeese]

I already wrote this in #35, but for reference, my test with lit-html V1.1.2 was to test issues with relative paths and .js extensions, specifically how lit-html.js did import statements like

import { defaultTemplateProcessor } from './lib/default-template-processor.js';

This PR is loading lit-html V2.0.2, which doesn't seem to import anything, although it's hard to tell because it's minimized.

If your goal is to make a test case then probably loading lit-html V1 is better.

In any case, please test your #39 against lit-html 1.1.2.