Previously the editor always opened Code.lu ( this was hardcodet with
#define FILENAME )

Now the last opened filename gets written to config.txt on save and is loaded
on startup. fgets pulls the name, strcspn strips the newline. (Revolutionary tech there 🔥🔥🔥)

After running a program or opening the menu the cursor was landing somewhere
random on screen. I fixed it by saving x and y with getxy() before switching modes,
and restoring it with gotoxy() .Then everithing is redrawn.
The cursor now comes back exactly where you left it. I thought this was implemented vom the start but it turns out it was not right 💀.

Added a proper README with a platform support table (Windows only) , step by step build instructions for CLion.