LibWeb/Tests: Add a basic test for a blob URL given to a Worker

Tests/LibWeb/Text/expected/Worker/Worker-blob.txt

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+Message received from worker: "WHF! :^)"

Tests/LibWeb/Text/input/Worker/Worker-blob.html

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+<script src="../include.js"></script>
+<script>
+    asyncTest((done) => {
+        const workerScript = `
+            self.onmessage = function(evt) {
+                self.postMessage('WHF! :^)');
+            };
+        `;
+        const blob = new Blob([workerScript], { type: 'application/javascript' });
+        const workerScriptURL = URL.createObjectURL(blob);
+        const worker = new Worker(workerScriptURL);
+
+        worker.onmessage = function(evt) {
+            println('Message received from worker: ' + JSON.stringify(evt.data));
+            done();
+        };
+
+        // Send a message to the worker
+        worker.postMessage('Hello from main script');
+    });
+</script>