ENGCOM-3917: Improve auth.json.sample #20416

 - Merge Pull Request #20416 from brendanfalkowski/magento2:feature/fix-auth-json
 - Merged commits:
   1. 359d82f
   2. 4d56b68
   3. 7d0f89d

Author: magento-engcom-team

auth.json.sample

@@ -1,8 +1,11 @@
 {
-   "http-basic": {
-      "repo.magento.com": {
-         "username": "<public-key>",
-         "password": "<private-key>"
-      }
-   }
+    "github-oauth": {
+        "github.com": "<github-personal-access-token>"
+    },
+    "http-basic": {
+        "repo.magento.com": {
+            "username": "<public-key>",
+            "password": "<private-key>"
+        }
+    }
 }