chore: migrate to flat config

packages/misskey-mahjong/eslint.config.js

@@ -0,0 +1,25 @@
+import tsParser from '@typescript-eslint/parser';
+import sharedConfig from '../shared/eslint.config.js';
+
+export default [
+	...sharedConfig,
+	{
+		ignores: [
+			'**/node_modules',
+			'built',
+			'coverage',
+			'jest.config.ts',
+		],
+	},
+	{
+		files: ['**/*.ts', '**/*.tsx'],
+		languageOptions: {
+			parserOptions: {
+				parser: tsParser,
+				project: ['./tsconfig.json'],
+				sourceType: 'module',
+				tsconfigRootDir: import.meta.dirname,
+			},
+		},
+	},
+];