Introduce acct directory

src/acct/parse.ts

@@ -0,0 +1,4 @@
+export default acct => {
+	const splitted = acct.split('@', 2);
+	return { username: splitted[0], host: splitted[1] || null };
+};

src/acct/render.ts

@@ -0,0 +1,3 @@
+export default user => {
+	return user.host === null ? user.username : `${user.username}@${user.host}`;
+};