Wiki improvement Suggestion: Example Koa middleware
Thanks for your work on this project!

The example Koa middleware in the [wiki](https://github.com/animir/node-rate-limiter-flexible/wiki/Koa-Middleware) will return a 429 response if any subsequent middleware (such as the route's main handler) throws an exception, not just if `rateLimiter.consume()` throws an exception. I believe replacing with the following code would be an improvement:
```js
app.use(async (ctx, next) => {
  try {
    await rateLimiter.consume(ctx.ip)
  } catch (rejRes) {
    ctx.status = 429
    ctx.body = 'Too Many Requests'
    return  // Subsequent middleware should only be invoked if rate limit check succeeded
  }
  await next()
})
```

and for reference, the current function in the wiki is as follows:
```js
app.use(async (ctx, next) => {
  try {
    await rateLimiter.consume(ctx.ip)
    next()
  } catch (rejRes) {
    ctx.status = 429
    ctx.body = 'Too Many Requests'
  }
})
```