Updates all CMS updates to use:
- Tailwind 3 (and the corresponding `tailwind.config.js` and PostCSS changes)
- `remark@14` and `remark-html@15` (and the corresponding ESM breaking changes)
- `date-fns` minor bump
Ensured all CMS examples were:
- Using `next/image`
- Not using `as` for `next/link` (no longer needed)
I realized while looking over this that the `autoprefixer` plugin isn't being used by postcss because it's not included in the `postcss.config.js`. Additionally, since `postcss-preset-env` doesn't support PostCSS 8 yet, and it includes PostCSS 7 as a dependency, I've removed that package.
There is an open issue to add PostCSS 8 support to `postcss-preset-env` [here](https://github.com/csstools/postcss-preset-env/issues/191). @kripod's comments on my other PR #20956 are what prompted me to check this out.
On a side note, it looks like all the CMS examples use Tailwind CSS v1 still, so that's something someone (possibly myself) could tackle later.
* update postcss.config.js to fix warnings
Return empty array if the condition is not met to avoid a null/undefined PostCSS plugin.
Related PR: https://github.com/zeit/next.js/pull/11366
* style: correct linting error
