docs(service-worker): describe how asset-/data-group order affects request handling (#38364)

The order of asset- and data-groups in `ngsw-config.json` affects how a
request is handled by the ServiceWorker. Previously, this was not
clearly documented.

This commit describes how the order of asset-/data-groups affects
request handling.

Closes #21189

PR Close #38364

aio/content/guide/service-worker-config.md

@@ -53,14 +53,27 @@ This field contains an array of asset groups, each of which defines a set of ass
 
 ```json
 {
-  "assetGroups": [{
+  "assetGroups": [
+    {
       ...
-  }, {
+    },
+    {
       ...
-  }]
+    }
+  ]
 }
 ```
 
+<div class="alert is-helpful">
+
+When the ServiceWorker handles a request, it checks asset groups in the order in which they appear in `ngsw-config.json`.
+The first asset group that matches the requested resource handles the request.
+
+It is recommended that you put the more specific asset groups higher in the list.
+For example, an asset group that matches `/foo.js` should appear before one that matches `*.js`.
+
+</div>
+
 Each asset group specifies both a group of resources and a policy that governs them. This policy determines when the resources are fetched and what happens when changes are detected.
 
 Asset groups follow the Typescript interface shown here:
@@ -123,6 +136,31 @@ These options are used to modify the matching behavior of requests. They are pas
 
 Unlike asset resources, data requests are not versioned along with the app. They're cached according to manually-configured policies that are more useful for situations such as API requests and other data dependencies.
 
+This field contains an array of data groups, each of which defines a set of data resources and the policy by which they are cached.
+
+```json
+{
+  "dataGroups": [
+    {
+      ...
+    },
+    {
+      ...
+    }
+  ]
+}
+```
+
+<div class="alert is-helpful">
+
+When the ServiceWorker handles a request, it checks data groups in the order in which they appear in `ngsw-config.json`.
+The first data group that matches the requested resource handles the request.
+
+It is recommended that you put the more specific data groups higher in the list.
+For example, a data group that matches `/api/foo.json` should appear before one that matches `/api/*.json`.
+
+</div>
+
 Data groups follow this Typescript interface:
 
 ```typescript