Relocate the configurations for Turbo and Stimulus to community-managed repos

[jaredcwhite]

Just as we did with Tailwind before, I'd like to remove the Bundled Configurations for Turbo and Stimulus and move those to a separate community-managed repo. This is in line with our general policy not to promote technologies maintained by 37signals, and on top of that, there's increasingly less need to reach for Turbo or Stimulus now that the native web platform has cross-document view transitions (no more need for Turbo Drive in most cases), fetch (it's trivial to submit forms via Ajax), and web components (which can replace Stimulus in many cases, as well as handle "actions")—plus other popular libraries like htmx & Alpine.js. (I'm also a big fan of i-html.)

[jaredcwhite]

Related: #970