Double encoding of query

seems that query is encoded one more time when hitting express.
I had to add this peace of code before passing event to module:
```js
exports.handler = (event, context) => {
Object.keys(event.queryStringParameters).forEach((key) => {
// eslint-disable-next-line no-param-reassign
event.queryStringParameters[key] = decodeURIComponent(event.queryStringParameters[key]);
});
awsServerlessExpress.proxy(server, event, context);
};
```

Start with the handler workaround in the issue and trace how event.queryStringParameters reaches awsServerlessExpress.proxy. Reproduce a query containing encoded characters through the AWS serverless Express path, compare the value received by Express, and confirm that callers no longer need to decode parameters before invoking the proxy.

Scritto dal modello di indicizzazione a partire dal testo della issue.