fix(popup): Allow SVG elements in focus calculations (#2331)

SVG elements should not be used as popup targets, but we shouldn't be restricting them. This change allows SVG elements to be valid elements when it comes to calculating focus returning and management in the popup system.

Fixes #2330

[category:Components]

modules/react/popup/lib/hooks/useReturnFocus.tsx

@@ -58,8 +58,8 @@ export const useReturnFocus = createElemPropsHook(usePopupModel)(model => {
   // should not return focus
   const onMouseDown = React.useCallback(
     (event: MouseEvent) => {
-      if (model.state.stackRef.current && event.target instanceof HTMLElement) {
-        if (!PopupStack.contains(model.state.stackRef.current, event.target)) {
+      if (model.state.stackRef.current && event.target instanceof Element) {
+        if (!PopupStack.contains(model.state.stackRef.current, event.target as HTMLElement)) {
           elementRef.current = event.target;
         }
       }
@@ -119,8 +119,8 @@ export const useReturnFocus = createElemPropsHook(usePopupModel)(model => {
       const activeElementOutsidePopupStack =
         document.activeElement !== document.body &&
         model.state.stackRef.current &&
-        document.activeElement instanceof HTMLElement &&
-        !PopupStack.contains(model.state.stackRef.current, document.activeElement);
+        document.activeElement instanceof Element &&
+        !PopupStack.contains(model.state.stackRef.current, document.activeElement as HTMLElement);
 
       if (activeElementOutsidePopupStack || requiresFocusChangeRef.current) {
         // We need to change focus _before_ the browser process the default action of picking a new