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/functions/function-missing-arg.js

@@ -0,0 +1,13 @@
+load("test-common.js");
+
+function foo(a, b) { return a + b; }
+
+try {
+    assert(isNaN(foo()) === true);
+    assert(isNaN(foo(1)) === true);
+    assert(foo(2, 3) === 5);
+    assert(foo(2, 3, 4) === 5);
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}