An input[type=file] element should have a FileList

We can specify files via input element. The specified files can be accessed from JavaScript via the input element's files attribute. This behavior is defined in [HTML standard](https://html.spec.whatwg.org/multipage/input.html#concept-input-type-file-selected) and [File API spec](https://w3c.github.io/FileAPI/#filelist-section), and also explained on [MDN Web docs](https://developer.mozilla.org/en-US/docs/Web/API/FileList).

I tried the following program with worker-dom and found that no filelist attribute is available on an input element.

~~~javascript
const container = document.createElement("div");
container.innerHTML = `

const fileInput = container.querySelector("input[type=file]");
fileInput.addEventListener("change", e => {
const parentNode = e.target.parentNode;
const input = e.target;
const span = document.createElement("span");
if (input.files && input.files[0]) {
span.textContent = input.files[0];
} else {
span.textContent = "FileList is not available";
}
parentNode.appendChild(span);
});

document.body.appendChild(container);
~~~

## Expected result

File name is displayed when I specified a file via the input element.

## Actual result

No file name is displayed as following screenshot.


Reproduce the provided JavaScript example with an input[type=file] element and compare its behavior with the HTML standard, File API specification, and MDN FileList documentation. Trace the worker-dom input element entry point and make input.files available as a FileList so the example displays the selected file name.

Written by the indexing model from the issue text.