fix: remove shebang line from index.ts (#44)

## Overview

It's OK for `index.ts`, but not for `index.js`. `"bin"` in
`package.json` is set to `lib/index.js`, and `ts-node` is not installed
with the npm package since it's a `devDependency`.

Fixes #41

src/index.ts

@@ -1,6 +1,3 @@
-#!/usr/bin/env node --loader ts-node/esm --no-warnings
-
-// eslint-disable-next-line n/shebang
 import { main } from "./main.js";
 
 await main();