Add hack

From Akuli/porcupine:
```py
# TODO: the next 3 lines are a hack?
# If they are really needed, why it isn't in sv-ttk by default?
main_window.option_add("*Text.highlightThickness", "0")
main_window.option_add("*Text.borderWidth", "2")
main_window.option_add("*Text.relief", "solid")
```