[css-flexbox][css-align] Proposal: `justify-items` and `justify-self` to align flex items that are alone on their line

Ok, I have to say that this is a very rough/raw idea, but the problem it would solve is a real one: there's currently no way to have a flex container with justify-content: space-between and flex-wrap: wrap and control the horizontal alignment ("justification"?) of the items that end up alone on their line (they are always start-aligned, at least in LTR). A workaround exists to make them end-aligned, but I couldn't find any to make them center-aligned. What if it was as simple as this?

.flex {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  justify-items: center; /* <-- this currently doesn't work; `justify-items` is ignored in flex layout */
}

Or, a more concrete example where we only want to center-align a specific item when it wraps:

<footer style="display: flex; flex-wrap: wrap; justify-content: space-between; gap: 1rem;">
  <nav>Nav content here</nav>
  <div>Social links here</div>
  <p style="justify-self: center; text-align: center;">
    Copyright © 2024 Example Company
  </p>
</footer>

Check out that example on Codepen. There is currently no way to center-align the copyright notice without using a media query, which is just sad.

Start with the flex-wrap and justify-content examples in the issue and the linked CodePen. Then review the CSS Flexbox and CSS Align behavior described by the issue for justify-items and justify-self; done means the proposed behavior has a clear Working Group decision and corresponding specification changes.