Does some stuff

src/lib/Categories.svelte

@@ -5,13 +5,15 @@
   export let categories: string[];
   export let selectedCategories: string[];
   export let toggleCategory: (category: string) => void;
+
+  const isSelected = (selected: string[], current: string) => selected.map((c) => c.toLocaleLowerCase()).includes(current.toLocaleLowerCase());
 </script>
 
 <div class="categories" transition:slide>
   {#each Object.keys(categories) as category}
     <Button
       action={() => toggleCategory(category)}
-      selected="{selectedCategories.includes(category)}"
+      selected="{isSelected(selectedCategories, category)}"
     >
     {category}
     </Button>