docs: baseConfig and overrideConfig can be arrays (eslint#18571)

docs/src/integrate/nodejs-api.md

@@ -140,9 +140,9 @@ The `ESLint` constructor takes an `options` object. If you omit the `options` ob
 
 * `options.allowInlineConfig` (`boolean`)<br>
   Default is `true`. If `false` is present, ESLint suppresses directive comments in source code. If this option is `false`, it overrides the `noInlineConfig` setting in your configurations.
-* `options.baseConfig` (`ConfigData | null`)<br>
+* `options.baseConfig` (`ConfigData | ConfigData[] | null`)<br>
   Default is `null`. [Configuration object], extended by all configurations used with this instance. You can use this option to define the default settings that will be used if your configuration files don't configure it.
-* `options.overrideConfig` (`ConfigData | null`)<br>
+* `options.overrideConfig` (`ConfigData | ConfigData[] | null`)<br>
   Default is `null`. [Configuration object], overrides all configurations used with this instance. You can use this option to define the settings that will be used even if your configuration files configure it.
 * `options.overrideConfigFile` (`string | boolean`)<br>
   Default is `false`. The path to a configuration file, overrides all configurations used with this instance. The `options.overrideConfig` option is applied after this option is applied.

lib/eslint/eslint.js

@@ -68,7 +68,7 @@ const { Retrier } = require("@humanwhocodes/retry");
  * The options with which to configure the ESLint instance.
  * @typedef {Object} ESLintOptions
  * @property {boolean} [allowInlineConfig] Enable or disable inline configuration comments.
- * @property {ConfigData} [baseConfig] Base config object, extended by all configs used with this instance
+ * @property {ConfigData|Array<ConfigData>} [baseConfig] Base config, extended by all configs used with this instance
  * @property {boolean} [cache] Enable result caching.
  * @property {string} [cacheLocation] The cache file to use instead of .eslintcache.
  * @property {"metadata" | "content"} [cacheStrategy] The strategy used to detect changed files.
@@ -79,7 +79,7 @@ const { Retrier } = require("@humanwhocodes/retry");
  * @property {boolean} [globInputPaths] Set to false to skip glob resolution of input file paths to lint (default: true). If false, each input file paths is assumed to be a non-glob path to an existing file.
  * @property {boolean} [ignore] False disables all ignore patterns except for the default ones.
  * @property {string[]} [ignorePatterns] Ignore file patterns to use in addition to config ignores. These patterns are relative to `cwd`.
- * @property {ConfigData} [overrideConfig] Override config object, overrides all configs used with this instance
+ * @property {ConfigData|Array<ConfigData>} [overrideConfig] Override config, overrides all configs used with this instance
  * @property {boolean|string} [overrideConfigFile] Searches for default config file when falsy;
  *      doesn't do any config file lookup when `true`; considered to be a config filename
  *      when a string.