Dev server is not rebuilding the HTML file when using templating

## Current behaviour 💣

Im using HTML templating to reduce the size of my HTML file. If I save `index.html`, the webpack dev server correctly rebuilds the file. However, if I save one of the template files, this does not happen.

## Expected behaviour ☀️

The HTML file should be rebuilt using the templates if a template file is saved.

### Reproduction Example 👾

- Initialise the HtmlWebpackPlugin
```ts
new HtmlWebpackPlugin({
filename: "./index.html",
template: resolve(__dirname, "../static/index.html"),
inject: "body",
}),
```
- Insert the template
```html

<%= compilation.assets["html/head.html"].source() %>

```
- Save the `head.html` file.
- The fill will not be rebuilt (sometimes it rebuilds for me but only once)
- My full source code is available here https://github.com/Miodec/monkeytype

I also tried setting it up on codesandbox but couldn't get the other HTML file to show up in `compilation.assets` https://codesandbox.io/s/html-webpack-plugin-5-x-alpha-forked-772ck7?file=/src/index.html

Hopefully this is okay, if not let me know.

## Environment 🖥

```
node -e "var os=require('os');console.log('Node.js ' + process.version + '\n' + os.platform() + ' ' + os.release())"

Node.js v16.13.2
darwin 21.4.0

npm --version

8.1.2

npm ls webpack

monkeytype@1.5.6 /Users/jackbartnik/Documents/Code/monkeytype
└── (empty)

npm ls html-webpack-plugin

monkeytype@1.5.6 /Users/jackbartnik/Documents/Code/monkeytype
└── (empty)

```

Reproduce the issue with the HtmlWebpackPlugin configuration, index.html, and the referenced head.html template from the linked example. Start by checking how saving head.html affects the webpack dev-server rebuild, then verify that saving a template consistently rebuilds index.html using the updated template.

Written by the indexing model from the issue text.