Use global value to check for current Shop product

Also add other stores types to hint on expected values

src/components/molecules/ShopLocationSwitcher.svelte

@@ -1,9 +1,9 @@
 <script lang="ts">
     import { goto } from '$app/navigation'
     import { getContext } from 'svelte'
+    import { shopCurrentProductSlug } from '$utils/stores/shop'
 
     export let isOver: boolean = false
-    export let currentProductSlug: string = undefined
 
     const { shopLocations } = getContext('shop')
 
@@ -29,7 +29,7 @@
         </svg>
         <select on:change={quickLocationChange}>
             {#each shopLocations as { name, slug }}
-                <option value={slug} selected={slug === currentProductSlug}>{name}</option>
+                <option value={slug} selected={slug === $shopCurrentProductSlug}>{name}</option>
             {/each}
         </select>
     </dd>

src/components/organisms/ShopHeader.svelte

@@ -127,6 +127,6 @@
     class:is-visible={scrolledPastIntro}
     class:is-overlaid={$cartOpen}
 >
-    <ShopLocationSwitcher currentProductSlug={product && product.location.slug} />
+    <ShopLocationSwitcher />
     <ButtonCart />
 </nav>