build: add TypeScript blocks to eslint.config.cjs

Add TypeScript-specific flat config blocks for `**/*.d.ts` and
`**/test/**/*.ts` files:

- Configure `@typescript-eslint/parser` with `parserOptions.project`
  pointing to the root `tsconfig.json`
- Register `@typescript-eslint`, `@stylistic/ts`, `jsdoc`, `import`,
  `expect-type`, and `stdlib` plugins
- Reuse the existing TypeScript rules from `etc/eslint/rules/typescript.js`
- Disable `jsdoc/require-jsdoc` for TypeScript test files

Ref: stdlib-js/metr-issue-tracker#54

Author: Planeshifter

eslint.config.cjs

@@ -20,12 +20,19 @@
 
 // MODULES //
 
+var path = require( 'path' );
 var globals = require( 'globals' );
+var tsParser = require( '@typescript-eslint/parser' );
+var tsPlugin = require( '@typescript-eslint/eslint-plugin' );
+var stylisticTs = require( '@stylistic/eslint-plugin-ts' );
 var pluginN = require( 'eslint-plugin-n' );
 var pluginCspell = require( '@cspell/eslint-plugin' );
 var pluginJsdoc = require( 'eslint-plugin-jsdoc' );
+var pluginImport = require( 'eslint-plugin-import' );
+var pluginExpectType = require( 'eslint-plugin-expect-type' );
 var stdlibPlugin = require( './lib/node_modules/@stdlib/_tools/eslint/rules/scripts/plugin.js' );
 var allRules = require( './etc/eslint/rules' );
+var tsRules = require( './etc/eslint/rules/typescript.js' );
 var overrides = require( './etc/eslint/overrides' );
 
 
@@ -158,5 +165,38 @@ module.exports = [
 			}],
 			'no-restricted-syntax': restrictedSyntaxConfig
 		}
+	},
+
+	// TypeScript declarations:
+	{
+		'files': [ '**/*.d.ts' ],
+		'languageOptions': {
+			'parser': tsParser,
+			'sourceType': 'module',
+			'parserOptions': {
+				'project': path.join( __dirname, 'tsconfig.json' )
+			},
+			'globals': {
+				...globals.browser,
+				...globals.node
+			}
+		},
+		'plugins': {
+			'@typescript-eslint': tsPlugin,
+			'@stylistic/ts': stylisticTs,
+			'jsdoc': pluginJsdoc,
+			'import': pluginImport,
+			'expect-type': pluginExpectType,
+			'stdlib': stdlibPlugin
+		},
+		'rules': tsRules
+	},
+
+	// TypeScript test files:
+	{
+		'files': [ '**/test/**/*.ts' ],
+		'rules': {
+			'jsdoc/require-jsdoc': 'off'
+		}
 	}
 ];