fix(opt): list luxon as a dependency

opt/package.json

@@ -33,8 +33,11 @@
 	"devDependencies": {
 		"c8": "^12.0.0",
 		"fast-check": "^4.10.2",
-		"luxon": "^3.5.0",
 		"undici": "^8.12.2"
 	},
-	"types": "types/index.d.ts"
+	"types": "types/index.d.ts",
+	"dependencies": {
+		"@types/luxon": "^3.7.6",
+		"luxon": "^3.5.0"
+	}
 }

opt/test/test.js

@@ -1,9 +1,28 @@
 const { deepStrictEqual, ok, strictEqual } = require('node:assert');
+const { readFileSync } = require('node:fs');
 const { describe, it } = require('node:test');
 const fc = require('fast-check');
 const { fetch: undiciFetch } = require('undici');
 const { DateTime } = require('luxon');
 const opt = require('../index');
+const { dependencies } = require('../package.json');
+
+describe('the published package', () => {
+	it('should list everything index.js requires in dependencies', () => {
+		const source = readFileSync(require.resolve('../index'), 'utf8');
+
+		const required = source
+			.matchAll(/require\('([^.'][^']*)'\)/g)
+			.map(([, name]) => name)
+			.toArray();
+
+		ok(required.length > 0);
+		deepStrictEqual(
+			required.filter((name) => !dependencies?.[name]),
+			[],
+		);
+	});
+});
 
 describe('the parseOptions module should return all correct defaults', async () => {
 	it('should return the default date', async () => {