@bem-react/pack: Add watch mode for rebuild

## Info

Need add watch flag for rebuild project after change files.

## Example

**cli usage**

```sh
pack build -w
```

**selective configuration**

```ts
module.exports = {
  plugins: [
    useTypeScriptPlugin({
      watch: true,
    }),
    useAssetsPlugin({
      watch: false,
    }),
  ],
}
```

For watching can be used `chokidar` library