Unicode support

### Expected behavior:
Can place UTF8 characters such as ⏲️ in a .html file and they render as-is after output

### Actual behavior:
`⏲️`

### Steps to reproduce the problem:
```
import StaticFileHandler from 'serverless-aws-static-file-handler';

import { dirname,join as pathjoin} from 'path';
import { fileURLToPath } from 'url';

const __dirname = dirname(fileURLToPath(import.meta.url));

const clientFilesPath = pathjoin(__dirname,"./public/")
const fileHandler = new StaticFileHandler(clientFilesPath);

export async function importTest(event,context){
return fileHandler.get(event, context);
}
```
where public/index.html is as above

### Environment:
serverless-aws-static-file-handler 4.0.2
node 18.12.1, framework 3.25.1 (local) 3.25.1v (global), plugin 6.2.2, SDK 4.3.2
Ubuntu 22.04 LTS