feat: moveup fab

src/components/MoveUpButton.svelte

@@ -0,0 +1,38 @@
+<script lang="ts">
+	import { mdiChevronDoubleUp } from '@mdi/js';
+	import Icon from 'mdi-svelte';
+	let y: number = 0;
+
+	$: enabled = y > 100;
+
+	function onClick() {
+		window.scrollTo({ top: 0, behavior: 'smooth' });
+	}
+</script>
+
+<svelte:window bind:scrollY={y} />
+
+{#if enabled}
+	<button on:click={onClick}><Icon path={mdiChevronDoubleUp} /></button>
+{/if}
+
+<style>
+	button:focus {
+		box-shadow: 0 0 5px var(--special-shadow-color);
+	}
+	button {
+		border-radius: 35px;
+		width: 48px;
+		height: 48px;
+		position: fixed;
+		bottom: 32px;
+		right: 32px;
+		color: var(--text-soft-color);
+		border: 2px solid var(--border-color);
+		background-color: var(--light-color);
+	}
+	button:hover {
+		color: var(--special-color);
+		border: 4px solid var(--border-color);
+	}
+</style>