Restore snapshot conditionals section to use-custom-images.md (#61507)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: drielenr

content/actions/how-tos/manage-runners/larger-runners/use-custom-images.md

@@ -94,6 +94,24 @@ jobs:
       # Add any steps to download and setup any dependencies here
 ```
 
+### Conditionals
+
+The `snapshot` keyword supports conditional execution using the `if` keyword around the snapshot mapping. You can use conditions to control when an image snapshot is created. For example, the following job skips image creation for tag builds.
+
+```yaml
+jobs: 
+  build:
+    runs-on: my-image-generation-runner
+    snapshot: 
+        if: {% raw %}${{ ! startsWith(github.ref, 'refs/tags/') }}{% endraw %}
+        image-name: my-custom-image
+        version: 2.*
+    steps:
+      # Add any steps to download and setup any dependencies here
+```
+
+For more information about the `if` keyword, see [AUTOTITLE](/actions/how-tos/write-workflows/choose-when-workflows-run/control-jobs-with-conditions).
+
 ## Versioning
 
 When you generate custom images, {% data variables.product.github %} automatically assigns version numbers to help you manage updates and track image history.