enlarged font for panel titles

src/constants.js

@@ -122,6 +122,7 @@ export const PLAYER_STARTING_TOOLS = [
 export const PANEL_WIDTH = 400;
 export const PANEL_HEIGHT = 300;
 export const PANEL_FONT_SIZE = 10;
+export const PANEL_TITLE_FONT_SIZE = 16;
 export const PANEL_BG_COLOR = '#666';
 export const PANEL_BORDER_COLOR = '#333';