Centralize Font Constants and Fix Highlight Refresh Logic

[ba6ul]

Currently, font sizes for Sudoku cells are hardcoded in multiple files (Main.gd and Highlighter.gd)

Steps
1.
Making 3 constant in settings.gd
CELL_FONT_NORMEL
CELL_FONT_NOTE
CELL_FONT_HIGHLIGHTED

Update just the matching number highlighter to get the feel of it

Updating the Normal font to something that works.