fix(api-reference): add missing Since and default in paginate section

* Add default for `page.size` and `pageSize` (see withastro/astro#11561)
* Add missing Since for `page.url.first` and `page.url.last` (see withastro/astro#11176)

src/content/docs/en/reference/api-reference.mdx

@@ -925,7 +925,7 @@ const { page } = Astro.props;
 - `/posts/[...page].astro` would generate the URLs `/posts`, `/posts/2`, `/posts/3`, etc.
 
 `paginate()` has the following arguments:
-- `pageSize` - The number of items shown per page
+- `pageSize` - The number of items shown per page (`10` by default)
 - `params` - Send additional parameters for creating dynamic routes
 - `props` - Send additional props to be available on each page
 
@@ -960,7 +960,8 @@ Index of last item on current page.
 ##### `page.size`
 
 <p>
-**Type:** `number`
+**Type:** `number`  
+**Default:** `10`
 </p>
 
 How many items per-page.
@@ -1015,6 +1016,8 @@ Get the URL of the next page (will be `undefined` if no more pages). If a value
 
 ##### `page.url.first`
 
+<p><Since v="4.12.0" /></p>
+
 <p>
 **Type:** `string | undefined`
 </p>
@@ -1023,6 +1026,8 @@ Get the URL of the first page (will be `undefined` if on page 1). If a value is
 
 ##### `page.url.last`
 
+<p><Since v="4.12.0" /></p>
+
 <p>
 **Type:** `string | undefined`
 </p>