fix(highlighting): theme IDs contain spaces

packages/highlightjs/src/themes.spec.ts

@@ -0,0 +1,10 @@
+import themeDefinitions from "./themes.js";
+import { describe, expect, it } from "vitest";
+
+describe("Themes", () => {
+    it("all IDs don't contain spaces", () => {
+        for (const id of Object.keys(themeDefinitions)) {
+            expect(id).not.toMatch(/\s/);
+        }
+    });
+});