Person pill avatar fallback (#472)

* avatar fallback

* changelog

---------

Co-authored-by: Alok Kumar <ialokkumarsingh0@gmail.com>

Author: Tishasoumya-02

frontend/packages/kitconcept-intranet/news/+avatarFallback.internal

@@ -0,0 +1 @@
+Avatar Fallback for personPill @Tishasoumya-02

frontend/packages/kitconcept-intranet/src/components/PersonPill/PersonPill.tsx

@@ -8,7 +8,7 @@ import {
   expandToBackendURL,
   flattenToAppURL,
 } from '@plone/volto/helpers/Url/Url';
-import personSVG from '@plone/volto/icons/user.svg';
+import AvatarFallback from '../../icons/avatar-fallback-silhouette.svg';
 
 type PersonPillProps = {
   id: string | undefined;
@@ -60,7 +60,7 @@ const PersonPill = ({
   ) : (
     <Icon
       className="person-pill-avatar"
-      name={personSVG}
+      name={AvatarFallback}
       size={compact ? '24px' : '40px'}
       style={{
         width: compact ? '24px' : '40px',