add jest-test-server, resolver and coverage

packages/overlayscrollbars/__tests__/puppeteer/Environment/index.test.ts

@@ -1,8 +1,8 @@
-import html from './__build__/build.html';
+import url from './__build__/build.html';
 
 describe('Environment', () => {
   beforeAll(async () => {
-    await page.setContent(html, { waitUntil: 'domcontentloaded' });
+    await page.goto(url);
   });
 
   it('should be titled "Environment"', async () => {

packages/overlayscrollbars/__tests__/puppeteer/Environment/index.ts

@@ -2,4 +2,6 @@ import { Environment } from 'environment';
 import 'some.scss';
 import 'some.css';
 
+document.body.append(JSON.stringify(new Environment()));
+
 export { Environment };