feat: injection of custom root element for react/vue/angular

[robertmain]

I was previously using this plugin to inject a custom div root element into the generated HTML page.

However, that plugin has not been maintained for several years and no longer works with Webpack 5. I know many others have wished for root element support in the issues, so the time felt right to stick a PR in to implement that.

It is possible to supply a template to the arguments either by string literal, or by location of an HTML file, however that can be a little cumbersome as you then have to keep the HTML file in your repo, when really it doesn't actually need to be at all.

Reviews/comments/thoughts/suggestions welcome.

[stale[bot]]

This issue had no activity for at least half a year. It's subject to automatic issue closing if there is no activity in the next 15 days.

[robertmain]

Bump. @jantimon