style: add opacity on default thumbnail

projects/solidify-frontend/src/lib/image/components/containers/image-upload-wrapper/image-upload-wrapper.container.html

@@ -18,7 +18,8 @@
     ></solidify-icon>
     <ng-template #defaultImg>
       <img [src]="preFallbackImage ? sanitizeUrl(preFallbackImage) : defaultImage"
-           alt="fallback-avatar"
+           alt="fallback-image"
+           class="fallback-image"
       >
     </ng-template>
   </ng-template>

projects/solidify-frontend/src/lib/image/components/containers/image-upload-wrapper/image-upload-wrapper.container.scss

@@ -11,6 +11,10 @@ $size-height: 300px;
     display: flex;
     justify-content: center;
     align-items: center;
+    
+    .fallback-image {
+      opacity: 0.2;
+    }
 
     &.is-readonly {
       cursor: initial;

projects/solidify-frontend/src/lib/image/components/presentationals/image-display/image-display.presentational.scss

@@ -20,6 +20,7 @@
     display: flex;
     align-items: center;
     justify-content: center;
+    opacity: 0.2;
   }
 
   .image {