(preact-iso) - avoid calling onLoadEnd on every render

[JoviDeCroock]

Fixes https://github.com/preactjs/wmr/issues/836

Ref solution: https://github.com/preactjs/wmr/pull/864/commits/d6c87e340538c341e7826b7b043dec03ddc306fd (ties into the effect on every render) State solution: https://github.com/preactjs/wmr/pull/864/commits/960364758bd818d8c00a482ef4c346c7adc05554 (avoids using effect on every render)

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 7e28300de70f048337c913c382863f53b228cde3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ---------- | ----- | | preact-iso | Minor |

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[github-actions[bot]]

Size Change: +126 B (+2%)

Total Size: 6.32 kB

Filename	Size	Change
packages/preact-iso/.dist/index.********.js	1.72 kB	+52 B (+3%)
packages/preact-iso/.dist/prerender.********.js	348 B	-2 B (-1%)
packages/preact-iso/router.js	2.54 kB	+76 B (+3%)

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `packages/preact-iso/hydrate.js` | 290 B | | `packages/preact-iso/index.js` | 195 B | | `packages/preact-iso/lazy.js` | 594 B | | `packages/preact-iso/prerender.js` | 629 B |

_{compressed-size-action}

[developit]

If we land this, I feel like we should also land a callback that fires after every successful route (sync or async), like onDidRoute. I often want to register a callback to do stuff like change title/reset scroll/etc