[prefetch.mdx] Adds a 'load' prefetch strategy

Link to withastro/astro#9513

src/content/docs/en/guides/prefetch.mdx

@@ -37,6 +37,7 @@ Astro supports 3 prefetch strategies for various use cases:
 - `hover` (default): Prefetch when you hover over or focus on the link.
 - `tap`: Prefetch just before you click on the link.
 - `viewport`: Prefetch as the links enter the viewport.
+- `load`: Prefetch the links on page load.
 
 You can specify a strategy for an individual link by passing it to the `data-astro-prefetch` attribute:
 
@@ -48,7 +49,7 @@ Each strategy is fine-tuned to only prefetch when needed and save your users' ba
 
 - If a visitor is using [data saver mode](https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/saveData) or has a [slow connection](https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/effectiveType), prefetch will fallback to the `tap` strategy.
 - Quickly hovering or scrolling over links will not prefetch them.
-- Links that use the `viewport` strategy are prefetched with a lower priority to avoid clogging up the network.
+- Links that use the `viewport` or `load` strategy are prefetched with a lower priority to avoid clogging up the network.
 
 ### Default prefetch strategy