[Docs] Link WindowEventMap definition in window events docs

[MannXo]

Summary

Fixes #9729

The EuiWindowEvent event prop is typed as keyof WindowEventMap, so the props table only ever showed that raw type name without explaining what it means or where to find the valid values. This adds a short sentence linking WindowEventMap to its actual definition so readers can find the exact accepted event names.

Note: WindowEventMap is a TypeScript-only interface (not a documented Web API), so there's no MDN page for it — the link points to the interface definition in the TypeScript repo, pinned to the typescript version EUI currently depends on (5.8.3) so the link stays accurate.

API Changes

N/A — docs-only change.

Screenshots

Before	After

Impact Assessment

• 🔴 Breaking changes
• 💅 Visual changes
• 🧪 Test impact
• 🔧 Hard to integrate

Impact level: 🟢 None

Release Readiness

• Documentation: Window events
• Figma
• Migration guide
• Adoption plan

QA instructions for reviewer

• Open the Window events docs page and confirm the new sentence renders correctly under "Basic example: closing a modal on escape"
• Confirm the WindowEventMap link resolves to the TypeScript interface definition

Checklist before marking Ready for Review

• Filled out all sections above
• QA: Tested light/dark modes, high contrast, mobile, Chrome/Safari/Edge/Firefox, keyboard-only, screen reader
• QA: Tested in CodeSandbox and Kibana
• QA: Tested docs changes
• Tests: Added/updated Jest, Cypress, and VRT
• Changelog: Added changelog entry (docs-only change per changelogs.md — skip-changelog label requested, see comment below; I don't have permission to self-apply it)
• Breaking changes

Reviewer checklist

• Approved Impact Assessment — Acceptable to merge given the consumer impact.
• Approved Release Readiness — Docs, Figma, and migration info are sufficient to ship.

[github-actions]

👋 Since this is a community submitted pull request, a Buildkite build has not been started automatically. Would an Elastic organization member please verify the contents of this pull request and kick off a build manually?

[MannXo]

This is a documentation-only change to packages/website/docs/, which per changelogs.md doesn't need a changelog entry. Could a maintainer add the skip-changelog label to bypass the CI check? I don't have permission to add labels myself as a community contributor.

[weronikaolejniczak]

@MannXo Instead of adding the link directly in the content, I would add a JSDoc comment for event which will automatically propagate to the prop table in the documentation.

eui/packages/eui/src/services/window_event/window_event.ts

Lines 13 to 16 in 5d0fffa

	interface Props<Ev extends EventNames> {
	event: Ev;
	handler: (this: Window, ev: WindowEventMap[Ev]) => any;
	}

[MannXo]

@MannXo Instead of adding the link directly in the content, I would add a JSDoc comment for event which will automatically propagate to the prop table in the documentation.

eui/packages/eui/src/services/window_event/window_event.ts

Lines 13 to 16 in 5d0fffa

	interface Props<Ev extends EventNames> {
	event: Ev;
	handler: (this: Window, ev: WindowEventMap[Ev]) => any;
	}

Reflected. see updated screenshot in the PR description