LibWeb: Implement TextEncoder.prototype.encode()

Author: https://github.com/linusg
Commit: f37d00c07b
Pull-request: https://github.com/SerenityOS/serenity/pull/11231
Reviewed-by: https://github.com/alimpfard

Userland/Libraries/LibWeb/Tests/Encoding/TextEncoder.prototype.encode.js

@@ -0,0 +1,28 @@
+describe("normal behavior", () => {
+    loadLocalPage("/res/html/misc/blank.html");
+
+    afterInitialPageLoad(page => {
+        test("Basic functionality", () => {
+            const textEncoder = new page.TextEncoder();
+
+            {
+                const typedArray = textEncoder.encode("");
+                expect(typedArray).toHaveLength(0);
+            }
+
+            {
+                const typedArray = textEncoder.encode("abc");
+                expect(typedArray).toHaveLength(3);
+                expect(Array.from(typedArray)).toEqual([97, 98, 99]);
+            }
+
+            {
+                const typedArray = textEncoder.encode("€");
+                expect(typedArray).toHaveLength(3);
+                expect(Array.from(typedArray)).toEqual([226, 130, 172]);
+                // [255, 254, 172, 32] in UTF-16, but TextEncoder always converts JS UTF-16 strings to UTF-8
+            }
+        });
+    });
+    waitForPageToLoad();
+});