Add additional option to include initialization script for Html.React

In my scenario I was using react component in a page that was rendered using partial views fetched via AJAX, so one call for `@Html.ReactInitJavaScript()` at the beginning was not enough. I wanted to run initialization script just after rendering server-side content and this additional flag seemed to fulfill my requirements.
I wonder if having this as a separate method adds value, it may be better to just inline the `Environment.CreateComponent` call in both of the methods below.