feat: prefer Config over FlatConfig when they're equal

Author: irsooti

recommended.d.ts

@@ -1,5 +1,17 @@
 import { Linter } from 'eslint';
 
-declare const recommendedConfig: Linter.FlatConfig;
+// prettier-ignore
+type IFEqual<A, B, X, Y> =
+  (<G>() => G extends A & G | G ? 1 : 2) extends
+  (<G>() => G extends B & G | G ? 1 : 2)
+    ? A
+    : B;
+
+declare const recommendedConfig: IFEqual<
+  Linter.Config,
+  Linter.FlatConfig,
+  Linter.Config,
+  Linter.FlatConfig
+>;
 
 export = recommendedConfig;