Remove instances of "Coming Soon"

Let's leave experimental code in place, but we want to change the language we're using to be more direct to developers.

- [ ] Remove Contentful from the home page installation section
- [ ] "Considering" frameworks and sources should be something like "Open for Contribution" (ideally shorter) with details about the issue, support for getting started, etc.
- [ ] Remove Vite example page (other examples we can add)

Start with the home page installation section and the Vite example page, then locate the text for frameworks and sources labeled “Considering.” Done means the Contentful reference and Vite example are removed, and the remaining wording is replaced with a shorter, more direct contribution-oriented label and supporting details.

Written by the indexing model from the issue text.