readd first-input in ww observe.ts

Author: Lms24

packages/browser-utils/src/metrics/web-vitals/lib/observe.ts

@@ -16,6 +16,7 @@
 
 interface PerformanceEntryMap {
   event: PerformanceEventTiming[];
+  'first-input': PerformanceEventTiming[];
   'layout-shift': LayoutShift[];
   'largest-contentful-paint': LargestContentfulPaint[];
   'long-animation-frame': PerformanceLongAnimationFrameTiming[];