Click Right Click in your editor window and select for 'Command Pallet' 
option

OR press CTRL+SHIFT+P and search for the option 'Enable Error Squiggle' 
and just click on it. Reference Image That's it! If you want to Disable 
Red Wavy underlines showed after syntax error, just Follow the above procedure 
and search for 'Disable Error Squiggle' and click on it.