FuzzJs: If the program successfully parsed, try running it

This should help us get a lot more coverage in LibJS.

Meta/Lagom/Fuzzers/FuzzJs.cpp

@@ -25,8 +25,10 @@
  */
 
 #include <AK/StringView.h>
+#include <LibJS/Interpreter.h>
 #include <LibJS/Lexer.h>
 #include <LibJS/Parser.h>
+#include <LibJS/Runtime/GlobalObject.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -35,6 +37,11 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     auto js = AK::StringView(static_cast<const unsigned char*>(data), size);
     auto lexer = JS::Lexer(js);
     auto parser = JS::Parser(lexer);
-    parser.parse_program();
+    auto program = parser.parse_program();
+    if (!parser.has_errors()) {
+        auto vm = JS::VM::create();
+        auto interpreter = JS::Interpreter::create<JS::GlobalObject>(*vm);
+        interpreter->run(interpreter->global_object(), *program);
+    }
     return 0;
 }