fix: React 19 clusterer infinite loop (#19) + SSR document crash

[w3di]

Two issues when using the package with React 19.

1. Infinite re-render loop in YMapCustomClusterer (fixes #19, related to #15)

Rendering <YMapCustomClusterer> under React 19 throws Maximum update depth exceeded and the page hangs.

Root cause: React 19 changed callback-ref semantics — refs are re-invoked null -> value on every render (not only mount/unmount). YMapCustomClusterer forwards ref to the reactified YMapClusterer, so under React 19 the reactified clusterer re-binds on every render and loops through its internal setState (onRender).

Confirmed by several users in #19 on React 19.2.0.

2. document is not defined during SSR

EventBus calls document.appendChild(...) in its constructor, and a module-level mapEventBus is created at import time. On the server (e.g. Next.js prerender) document does not exist, so importing the package throws.

Fix

• YMapCustomClusterer: forward ref only on React <= 18 (parseInt(React.version, 10) < 19). On React 18 the imperative clusterer handle keeps working exactly as before; on React 19 the ref is skipped to avoid the infinite loop. This keeps backward compatibility and only changes behaviour where it currently crashes.
• EventBus: create the underlying EventTarget lazily via a getter, so the constructor no longer touches document at import time.

Source-only changes; npm run build (vite build && tsc) passes.

Note

On React 19 the ref (imperative YMapClusterer handle) is not exposed, since forwarding it is exactly what triggers the loop. If you prefer a different approach for exposing the handle on React 19, happy to adjust.