LibJS: Disallow 'continue' & 'break' outside of their respective scopes

'continue' is no longer allowed outside of a loop, and an unlabeled
'break' is not longer allowed outside of a loop or switch statement.
Labeled 'break' statements are still allowed everywhere, even if the
label does not exist.

Libraries/LibJS/Parser.h

@@ -159,6 +159,8 @@ private:
         bool m_allow_super_property_lookup { false };
         bool m_allow_super_constructor_call { false };
         bool m_in_function_context { false };
+        bool m_in_break_context { false };
+        bool m_in_continue_context { false };
 
         explicit ParserState(Lexer);
     };