Add JSX.ElementChildrenAttribute change to TypeScript 5.8 release notes

Review PR 60880 and issue 61354 to confirm the JSX.ElementChildrenAttribute behavior change, then compare it with the TypeScript 5.8 release notes. Update the 5.8 release-notes page to describe the breaking change and its effect on children inference, using the reported twrl example as context.

🔎 Search Terms

tsx, jsx, children, 5.8

🕗 Version & Regression Information

• This changed between versions 5.7.3 and 5.8
• This changed in commit or PR 60880

⏯ Playground Link

No response

💻 Code

declare global {
  namespace JSX {
    type Element = HTMLElement; /* return type for 'jsx()' */

    /* accepted element tags & attributes */
    type IntrinsicElements = {
      /* All HTML elements */
      [Tag in keyof HTMLElementTagNameMap]: {
        [T in HTMLElementStringAttributes<Tag>]?: string | Dyn<string>;
      } & {
        [T in HTMLElementNumberAttributes<Tag>]?: number | Dyn<number>;
      } & (Tag extends keyof TwrlOverrides ? TwrlOverrides[Tag] : {}) & {
          style?: string /* note: This should probably be CSSStyleDeclaration */;
          // BREAKS HERE without this: children?: Children /* defines the type of children */;
        };
    };
  }
}

🙁 Actual behavior

The breaking change is not listed in the 5.8 Release Notes

🙂 Expected behavior

The breaking change should be listed in the 5.8 Release Notes

Additional information about the issue

I ran into issues when upgrading TypeScript and narrowed it down to 5.7.3 to 5.8. The issues is that children is not inferred by default.

Luckily I came across this discussion: https://github.com/microsoft/TypeScript/issues/61354

This led me to this PR: https://github.com/microsoft/TypeScript/pull/60880

It would have been much faster if the (breaking) change had been mentioned in the 5.8 release notes. Moreover, one (apparent?) side effect of #61354 is that children does not have a default anymore (i.e. if JSX.ElementChildrenAttribute is not set, pre-5.8 children would be accepted; post-5.8 not anymore).

Here's the JSX implementation that surfaced the issue for me:

declare global {
  namespace JSX {
    type Element = HTMLElement; /* return type for 'jsx()' */

    /* accepted element tags & attributes */
    type IntrinsicElements = {
      /* All HTML elements */
      [Tag in keyof HTMLElementTagNameMap]: {
        [T in HTMLElementStringAttributes<Tag>]?: string | Dyn<string>;
      } & {
        [T in HTMLElementNumberAttributes<Tag>]?: number | Dyn<number>;
      } & (Tag extends keyof TwrlOverrides ? TwrlOverrides[Tag] : {}) & {
          style?: string /* note: This should probably be CSSStyleDeclaration */;
          children?: Children /* defines the type of children */; // <- this is now REQUIRED
        };
    };
  }
}

Fix: https://github.com/nmattia/twrl/commit/d83fde44202536c52f2816094fdcc4910c945c85#diff-8e3158c55134a198f9c40ac714ce358df04312a9ca77d7726e1813fb2ba5b5c0R34