docs: add datepicker component story (#156)

* docs: datepicker component document (#118)

* fix(docs): remove reactivity in datepicker (#118)

src/components/DatePicker/DatePicker.story.svelte

@@ -0,0 +1,14 @@
+<script lang="ts">
+	import type { Hst } from '@histoire/plugin-svelte';
+	import DatePicker from './DatePicker.svelte';
+	export let Hst: Hst;
+
+	let selectedDate = new Date();
+	const handleSelectDate = (date: Date) => {
+		selectedDate = date;
+	};
+</script>
+
+<Hst.Story title="DatePicker" layout={{ type: 'single' }}>
+	<DatePicker {selectedDate} {handleSelectDate} />
+</Hst.Story>