[LoadingButton] LoadingButton accessibility of the pending state

First off, I love the new <LoadingButton /> component and I'm excited to use it!

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

The <LoadingButton /> is currently in the disabled state when pending is applied and is not marked aria-busy (not sure if this is necessary or appropriate for this use-case).

Expected Behavior 🤔

Because disabling the button would revert focus back to the document body, I would expect that there would be another way to prevent form submission or clicks without disabling the button itself. I also wonder if it's appropriate to add an aria-busy designation.

Steps to Reproduce 🕹

This can be seen in the docs.

Proposal

One thing I've tried is adding aria-busy and updating the click handler as to prevent the default behavior on click:

onClick={e => {
  if (pending) {
    // Prevent form submission
    e.preventDefault();
    return;
  }

  onClick(e);
}}

Start with the LoadingButton component and the loading-buttons example in the linked documentation, reproducing the pending-state focus and submission behavior. Review the current pending-state interaction and accessibility semantics, then confirm the chosen behavior preserves focus, prevents unintended activation, and provides appropriate busy-state signaling.