packages,plugins: add package documentation

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/config-loader/api-report.md

@@ -73,6 +73,4 @@ export type TransformFunc<T extends number | string | boolean> = (
     visibility: ConfigVisibility;
   },
 ) => T | undefined;
-
-// (No @packageDocumentation comment for this package)
 ```

packages/config-loader/src/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+/**
+ * Config loading functionality used by Backstage backend, and CLI
+ *
+ * @packageDocumentation
+ */
+
 export { readEnvConfig, loadConfigSchema, mergeConfigSchemas } from './lib';
 export type {
   ConfigSchema,