feat(isac): support deferred item icons

src/lib/components/BuilderRadioGrid.svelte

@@ -1,4 +1,6 @@
 <script lang="ts">
+	import ItemIcon from './ItemIcon.svelte';
+
 	let {
 		label,
 		name,
@@ -42,7 +44,7 @@
 			<label title={item.name}>
 				<input type="radio" {name} value={item.id} checked={value === item.id} {required} aria-label={item.name} onchange={() => choose(item.id)}/>
 				<span>
-					{#if item.iconUrl}<img src={item.iconUrl} alt=""/>{:else}<i>{item.name.slice(0,2).toUpperCase()}</i>{/if}
+					<ItemIcon src={item.iconUrl} alt=""/>
 					<b>{item.name}</b>
 					{#if item.category}<small>{item.category}</small>{/if}
 				</span>