adding sonarJS to our ESLint to evaluate it

[helms-charity]

Sonarjs
First I tested adding the SonarQube extension to Cursor (formerly SonarLint, which I used in previous AEM maven projects). It is very verbose and opinionated in what it checks (and I found some false positives) so filtering by 'high severity' was helpful.

But then I realized SonarJS as an ESlint plugin existed, which I am adding here. It is closer to finding the things I expected. (rules: https://github.com/SonarSource/SonarJS/blob/master/packages/jsts/src/rules/README.md#rules but they are different than what SonarQube found, and I'm not seeing any non-sanitized inner.HTML being flagged for XSS.

update package.json and package-lock.json
I noticed our versions of some items weren't updated with the latest Xwalk boilerplate repo, so I updated those too.

update README.md
I added a mention of the sonarJS and also a troubleshooting step to fix broken stylelint rules config.

remove old buttons test.html file
Fix #680

Test URLs:

• Before: https://main--idfc--aemsites.aem.page/
• After: https://680-sonarjs--idfc--aemsites.aem.page/

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Commits

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