ci: Set GitHub reporter for Playwright tests (#1673)

- Add the `github` reporter to add annotations directly in our code when
playwright tests fail
- See an example summary report from a previous run:
https://github.com/deephaven/web-client-ui/actions/runs/7121141960?pr=1673
- The annotations show up in the Summary, along with the HTML report
that you can download:

![image](https://github.com/deephaven/web-client-ui/assets/4505624/02a7df03-11fb-46fe-83fd-2c12e15489e6)
- Annotations also show up in the Files Changed tab, annotating the test
case explicitly that failed:

![image](https://github.com/deephaven/web-client-ui/assets/4505624/28c07ea6-b2e3-4118-868d-5a7cc450f2c7)

playwright-ci.config.ts

@@ -11,6 +11,7 @@ const config: PlaywrightTestConfig = {
     timeout: 60 * 1000,
     reuseExistingServer: false,
   },
+  reporter: [['github'], ['html']],
 };
 
 export default config;