feat(highlightjs): add test

packages/highlightjs/src/syntax_highlighting.spec.ts

@@ -0,0 +1,14 @@
+import { describe, it } from "vitest";
+import definitions from "./syntax_highlighting.js";
+
+describe("Syntax highlighting definitions", () => {
+    it("every entry is readable", async () => {
+        for (const [ mime, mapping ] of Object.entries(definitions)) {
+            if (mapping === null) {
+                continue;
+            }
+
+            await mapping.loader;
+        }
+    });
+});