Additional warning messages

[vicchig]

@MajeedKazemi do we want to include these?

1. I remember we wanted to have the pop-up messages appear when the user attempts to type an invalid character in a variable identifier.
   Currently, it highlights it in red and does not allow the user to insert the character. Do we still want to add these?

2. Do we want incomplete code to say something when you hover over it? Currently we just put a general statement in the console, but for example, Pycharm would say "Expression Expected" when you hover over such a warning.

Personally, I think we should add 1. 2. might require a bit too many changes.