Reduce JS payload by ~300KB (15% reduction)

GitHub Issue #2403 - ifmeorg/ifme

Optimize the JavaScript bundle size by removing unnecessary dependencies:

1. Remove html-react-parser (~200KB) and replace with dangerouslySetInnerHTML. DOMPurify still sanitizes everything so it remains safe.
2. Remove ES5 polyfills (~100KB) from webpack entry since modern browsers don't need them. Babel handles the necessary polyfills.

Total estimated savings: ~300KB (15% reduction). This should improve mobile performance score from approximately 40 to ~55.