fix: declare the default export of the package index

`index.mjs` has a single default export, an object mapping each property
type to its list of directories, but `index.d.mts` declared named
exports instead, so `import dirs from '@unicode/unicode-X'` failed to
type-check. The declaration now describes the default export with one
`readonly <Type>: string[]` property per type. A test checks that the
declared keys match the object exported at runtime.

Assisted-By: Claude Fable 5.1
Issue: #109

Author: JLHwung

index.mjs

@@ -328,9 +328,15 @@ const generateData = async (version) => {
 	);
 	fs.writeFileSync(
 		path.resolve(__dirname, `output/unicode-${version}/index.d.mts`),
-		Object.keys(dirMap)
-			.map((key) => `export const ${key}: string[];`)
-			.join('\n'),
+		// `index.mjs` has a single default export: an object mapping each
+		// property type to the list of its directories.
+		[
+			'declare const data: {',
+			...Object.keys(dirMap).map((key) => `\treadonly ${key}: string[];`),
+			'};',
+			'export default data;',
+			'',
+		].join('\n'),
 	);
 	fs.writeFileSync(
 		path.resolve(__dirname, `output/unicode-${version}/package.json`),

tests/tests.mjs

@@ -165,6 +165,16 @@ suite(`The generated latest Unicode js`, () => {
 			}
 		}
 	});
+	test('index.d.mts should declare the default export of index.mjs', async (t) => {
+		const root = path.resolve(__dirname, '..', 'output', `unicode-${newest}`);
+		const { default: data } = await import(path.join(root, 'index.mjs'));
+		const declaration = fs.readFileSync(path.join(root, 'index.d.mts'), 'utf8');
+		t.assert.match(declaration, /^export default data;$/m);
+		const declaredKeys = [
+			...declaration.matchAll(/^\treadonly (\w+): string\[\];$/gm),
+		].map((m) => m[1]);
+		t.assert.deepStrictEqual(declaredKeys, Object.keys(data));
+	});
 	test('type declarations should be shared via typesVersions', async (t) => {
 		const root = path.resolve(__dirname, '..', 'output', `unicode-${newest}`);
 		const pkg = JSON.parse(fs.readFileSync(path.join(root, 'package.json')));