[eslint] CLIEngine ignorePattern can be a string or string[] (#25197)

types/eslint/eslint-tests.ts

@@ -456,6 +456,7 @@ cli = new CLIEngine({ globals: ['foo'] });
 cli = new CLIEngine({ ignore: true });
 cli = new CLIEngine({ ignorePath: 'foo' });
 cli = new CLIEngine({ ignorePattern: 'foo' });
+cli = new CLIEngine({ ignorePattern: ['foo', 'bar'] });
 cli = new CLIEngine({ useEslintrc: false });
 cli = new CLIEngine({ parserOptions: {} });
 cli = new CLIEngine({ plugins: ['foo'] });

types/eslint/index.d.ts

@@ -2,6 +2,7 @@
 // Project: https://eslint.org
 // Definitions by: Pierre-Marie Dartus <https://github.com/pmdartus>
 //                 Jed Fox <https://github.com/j-f1>
+//                 Saad Quadri <https://github.com/saadq>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
@@ -491,7 +492,7 @@ export namespace CLIEngine {
         globals?: string[];
         ignore?: boolean;
         ignorePath?: string;
-        ignorePattern?: string;
+        ignorePattern?: string | string[];
         useEslintrc?: boolean;
         parser?: string;
         parserOptions?: Linter.ParserOptions;