common: add fullTime helper

js/src/common/helpers/fullTime.tsx

@@ -0,0 +1,16 @@
+/**
+ * The `fullTime` helper displays a formatted time string wrapped in a <time>
+ * tag.
+ */
+export default function fullTime(time: Date) {
+    const mo = dayjs(time);
+
+    const datetime = mo.format();
+    const full = mo.format('LLLL');
+
+    return (
+        <time pubdate datetime={datetime}>
+            {full}
+        </time>
+    );
+}