feat: add override of defining one item of flat config (#148)

Co-authored-by: Shinigami <[email protected]>

Author: sxzz

src/flat-config/index.d.ts

@@ -9,7 +9,7 @@ import type { LinterOptions } from './linter-options';
  *
  * @see [Configuration Files (New)](https://eslint.org/docs/latest/user-guide/configuring/configuration-files-new)
  */
-export interface FlatESLintConfig {
+export interface FlatESLintConfigItem {
   /**
    * An array of glob patterns indicating the files that the configuration object should apply to. If not specified, the configuration object applies to all files.
    *
@@ -67,4 +67,5 @@ export type PredefinedConfig = LiteralUnion<
   'eslint:recommended' | 'eslint:all'
 >;
 
-export type FlatESLintConfigs = Array<FlatESLintConfig | PredefinedConfig>;
+export type FlatESLintConfig = FlatESLintConfigItem | PredefinedConfig;
+export type FlatESLintConfigs = Array<FlatESLintConfig>;

src/index.d.ts

@@ -1,5 +1,5 @@
 import type { ESLintConfig } from './config';
-import type { FlatESLintConfigs } from './flat-config';
+import type { FlatESLintConfig, FlatESLintConfigs } from './flat-config';
 
 /**
  * Define an ESLint config.
@@ -9,6 +9,16 @@ import type { FlatESLintConfigs } from './flat-config';
  */
 export function defineConfig(config: ESLintConfig): ESLintConfig;
 
+/**
+ * Define an item of Flat ESLint config.
+ *
+ * @see [Configuration Files (New)](https://eslint.org/docs/latest/user-guide/configuring/configuration-files-new)
+ *
+ * @param config an item of Flat ESLint config.
+ * @returns an item of Flat ESLint config.
+ */
+export function defineConfig(config: FlatESLintConfig): FlatESLintConfig;
+
 /**
  * Define a flat ESLint config.
  *