LibJS: Add support for JSON modules

We now have one supported assertion: 'type' if that is 'json' we attempt
to parse the module as JSON.

Userland/Libraries/LibJS/Tests/modules/json-modules.js

@@ -0,0 +1,34 @@
+describe("basic behavior", () => {
+    test("can import json modules", () => {
+        let passed = false;
+        let error = null;
+        let result = null;
+
+        import("./json-module.json", { assert: { type: "json" } })
+            .then(jsonObj => {
+                passed = true;
+                result = jsonObj;
+            })
+            .catch(err => {
+                error = err;
+            });
+
+        runQueuedPromiseJobs();
+
+        if (error) throw error;
+
+        console.log(JSON.stringify(result));
+        expect(passed).toBeTrue();
+
+        expect(result).not.toBeNull();
+        expect(result).not.toBeUndefined();
+
+        const jsonResult = result.default;
+        expect(jsonResult).not.toBeNull();
+        expect(jsonResult).not.toBeUndefined();
+
+        expect(jsonResult).toHaveProperty("value", "value");
+        expect(jsonResult).toHaveProperty("array", [1, 2, 3]);
+        expect(jsonResult).toHaveProperty("map", { innerValue: "innerValue" });
+    });
+});