Add section on experimental cache to Content Collection page (#5312)

Co-authored-by: Sarah Rainsberger <[email protected]>

src/content/docs/en/guides/content-collections.mdx

@@ -9,6 +9,7 @@ import FileTree from '~/components/FileTree.astro'
 import Since from '~/components/Since.astro'
 import TypeScriptSettingTabs from '~/components/tabs/TypeScriptSettingTabs.astro'
 import RecipeLinks from "~/components/RecipeLinks.astro"
+import Badge from "~/components/Badge.astro"
 
 
 <p>
@@ -542,6 +543,21 @@ If you have an existing Astro project, such as a blog, that uses Markdown or MDX
 
 See how to convert a basic blog example from `src/pages/posts/` to `src/content/posts` in our [step-by-step tutorial](/en/tutorials/add-content-collections/) that uses the codebase from [the Build a Blog tutorial's finished project](https://github.com/withastro/blog-tutorial-demo).
 
+## Enabling Build Caching
+
+<p><Since v="3.5.0" /><Badge>Experimental</Badge></p>
+
+If you are working with large collections, you may wish to enable cached builds with the [`experimental.contentCollectionCache`](/en/reference/configuration-reference/#experimentalcontentcollectioncache) flag. This experimental feature optimizes Astro's build process, enabling unchanged collections to be stored and reused between builds.
+
+In many cases, this can lead to significant build performance improvements.
+
+While this feature stabilizes, you may run into issues with the stored cache. You can always reset your build cache by running the following command:
+
+```
+npm run astro build -- --force
+```
+
+
 ## Modifying Frontmatter with Remark
 
 :::caution