LibJS: Add "name" property to functions

Author: https://github.com/linusg
Commit: 99be27b4a1
Pull-request: https://github.com/SerenityOS/serenity/pull/2068

Libraries/LibJS/Tests/Date.js

@@ -0,0 +1,11 @@
+load("test-common.js");
+
+try {
+    assert(Date.length === 7);
+    assert(Date.name === "Date");
+    assert(Date.prototype.length === undefined);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}