fix(client): overlay not appearing when multiple vite clients were loaded

[seokju-na]

Description

Vite is creating a custom elemtn with <vite-error-overlay> to display error overlay.

If the vite client is loaded multiple times (e.g. in the case of Micro-Frontend architecture), there is an issue while creating error overlay from second vite client because creating custom element without defining into custom elements registry causes error. (below screenshot is error from chrome browser)

src/client/overlay.ts:

export const overlayId = 'vite-error-overlay'
const { customElements } = globalThis // Ensure `customElements` is defined before the next line.
if (customElements && !customElements.get(overlayId)) {
  customElements.define(overlayId, ErrorOverlay)
}

Fix this by get the constructor of ErrorOverlay from custom element registry if already defined.

Although it may not be the expected behavior for the vite client to be loaded multiple times, this PR will be helpful as there are cases where the ErrorOverlay singleton cannot be guaranteed.