Switch xml2json to xml2js in tooling

[dougwilson]

Additional description

So this is related to (but not the final fix for) #1366 . Typically Windows users will not have python and a g++ compiler tool chain installed in order to compile native addons. A lot of modules work-around this issue by offering pre-compiled addons (like node-sass), but node-expat (a dependency of xml2json) does not.

Since this is just in some tooling and I was able to use the popular xml2js to fill in with the same functionality, I thought this may be another way to help improve the Windows contributor experience.

Pull Request Review checklist (do not remove)

• npm run lint:fix has been run and linting passes.
• Mocha, Jest (Storyshots), and components/component-docs.json CI tests pass (npm test).
• Tests have been added for new props to prevent regressions in the future. See readme.
• Review the appropriate Storybook stories. Open http://localhost:9001/.
• Review tests are passing in the browser. Open http://localhost:8001/.
• Review markup conforms to SLDS by looking at DOM snapshot strings.
• Add year-first date and commit SHA to last-slds-markup-review in package.json and push.
• Request a review of the deployed Heroku app by the Salesforce UX Accessibility Team.
• Add year-first review date, and commit SHA, last-accessibility-review, to package.json and push.
• While the contributor's branch is checked out, run npm run local-update within locally cloned site repo to confirm the site will function correctly at the next release.

[interactivellama]

Just needs npm run lint:fix I'll think we'll be good.

[salesforce-cla]

Thanks for the contribution! It looks like @dougwilson is an internal user so signing the CLA is not required. However, we need to confirm this.