Export the defaultConfigLoader (#3603)

.changeset/tall-hairs-switch.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core': patch
+---
+
+Export the `defaultConfigLoader` implementation

packages/core/src/api-wrappers/index.ts

@@ -14,4 +14,4 @@
  * limitations under the License.
  */
 
-export { createApp } from './createApp';
+export { createApp, defaultConfigLoader } from './createApp';