Add configuration docs

Author: DuckThom

docs/configuration.md

@@ -0,0 +1,31 @@
+# Configuration
+
+The published configuration file (`config/importer.php`) contains 2 arrays: `importers` and `runners`.
+Both arrays should contain a key `default`, which is the key that will be used when no specific importer/runner is specified.
+
+## Example:
+
+```php
+return [
+    /***********************************************************
+     * Importers are used for defining specific import tasks
+     * For instance, a ProductImporter could import a file with
+     * products into a table.
+     ***********************************************************/
+    'importers' => [
+        'default' => App\Importers\ProductImporter::class,
+        'user' => App\Importers\UserImporter::class
+    ],
+
+    /***********************************************************
+     * Runners are used for looping through the file
+     * The default is a CSV runner which will loop though
+     * CSV files line-by-line. A runner uses an importer to get
+     * import specific settings like the model class.
+     ***********************************************************/
+    'runners' => [
+        'default' => \Luna\Importer\Runners\CsvRunner::class
+        'xml' => App\Runners\XmlRunner::class
+    ]
+];
+```