Fix PostCard responsive and add small size variant

src/components/molecules/PostCard.svelte

@@ -6,14 +6,22 @@
     export let region: string = undefined
     export let country: string
     export let flagId: string
+    export let size: string = undefined
+
+    const className = 'postcard'
+    $: classes = [
+        className,
+        ...[size].map(variant => variant && `${className}--${variant}`),
+        $$props.class
+    ].join(' ').trim()
 </script>
 
-<div class="postcard">
+<div class={classes}>
     <div class="postcard__left">
-        <h3 class="postcard__country">
+        <p class="postcard__country">
             <span>Houses of</span><br>
             <strong class="title-country__purple">{country}</strong>
-        </h3>
+        </p>
     </div>
     <div class="postcard__right">
         <div class="postcard__stamp">