stopPropagation for mousedown and click in AnchoredOverlay (#1206)

Co-authored-by: dgreif <dustin.greif@gmail.com>

Author: VanAnderson

.changeset/violet-geese-speak.md

@@ -0,0 +1,5 @@
+---
+"@primer/components": patch
+---
+
+stopPropagation for mousedown and click in AnchoredOverlay based components

src/AnchoredOverlay/AnchoredOverlay.tsx

@@ -5,6 +5,10 @@ import {useFocusZone} from '../hooks/useFocusZone'
 import {useAnchoredPosition, useRenderForcingRef} from '../hooks'
 import {uniqueId} from '../utils/uniqueId'
 
+function stopPropagation(event: React.UIEvent) {
+  event.stopPropagation()
+}
+
 export interface AnchoredOverlayProps {
   /**
    * A custom function component used to render the anchor element.
@@ -117,6 +121,8 @@ export const AnchoredOverlay: React.FC<AnchoredOverlayProps> = ({renderAnchor, c
           ref={updateOverlayRef}
           role="listbox"
           visibility={position ? 'visible' : 'hidden'}
+          onMouseDown={stopPropagation}
+          onClick={stopPropagation}
           {...overlayPosition}
         >
           {children}