Legacy build doesn't use html template

Just migrated a large project that was using a custom version of https://github.com/thereactivestack-legacy to your package and everything seems to work... except web.browser.legacy production bundles :)

For some reason the html created by
```
new HtmlWebpackPlugin({
template: './client/main.html',
base: '/'
}),
```
does not appear. I just get a bare `` and `` with links to css and js. Any ideas or pointers to debug this?

Start with the web.browser.legacy production build and the HtmlWebpackPlugin configuration shown in the report, then trace whether ./client/main.html is passed to that build. Done means the generated HTML contains the template's content rather than only and with asset links; no test or repository file is named in the report.

Written by the indexing model from the issue text.