Use some sort of debugger for code

[erwindenboer]

Hello,

It would be nice to highlight some line of code like a debugger when using the code Mobject. For example, while explaining pointers, it can be nice to highlight one particular line of code for what the variables are at that moment. For now, Transform can be used, but that makes it harder to keep track of where you are in a code snippet.

For now the following is used:
`from manim import *

     class CodeFromString(Scene):
     def construct(self):
     code = '''
     void main(void)
     {
         int a = 0;
         int b = 1;
         int *p = &a;
     }
     '''
    rendered_code = Code(code=code, tab_width=4, background="window", language="c", font="Monospace")

    self.play(FadeIn(rendered_code))` 

But I would like to highlight the line int a =0 such that I can explain what this code means in memory.