LibJS: Reorganize tests into subfolders

Author: https://github.com/mattco98
Commit: 4c48c9d69d
Pull-request: https://github.com/SerenityOS/serenity/pull/2681
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/builtins/JSON/JSON.parse-reviver.js

@@ -0,0 +1,15 @@
+load("test-common.js");
+
+try {
+    let string = `{"var1":10,"var2":"hello","var3":{"nested":5}}`;
+
+    let object = JSON.parse(string, (key, value) => typeof value === "number" ? value * 2 : value);
+    assertDeepEquals(object, { var1: 20, var2: "hello", var3: { nested: 10 } });
+
+    object = JSON.parse(string, (key, value) => typeof value === "number" ? undefined : value);
+    assertDeepEquals(object, { var2: "hello", var3: {} });
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}