Improved supports for in-app/game notifications and toasts

[BenCheung0422]

This feature is reserved for future use. This adds a support for in-app notifications, where toasts in the screen. It is different from in-game notifications, bare text only, as this includes a frame, and the color can be changed. This is important when there are some alerts, warnings and important information needed to notify the users.

I have several ideas about box popups and notifications: (fading is not supported right now)

• App status bar with icons (~~fade in~~appear ~~fade out~~disappear) - quick inspections about status (top bar near top-right)
• Toast notifications (slide in slide out) - quick informative notification (near top-right/bottom-right corner sliding on side)
• Bottom slide popup (slide in slide out) - app tool bar? But currently there is no such possible uses. (near bottom-right corner sliding on bottom)

Position for toasts may be configurable to upper or lower positions (also for each type of toast notification?).

Additionally, achievement unlocking toast is added to replace the text-only notifications regarding unlocking achievements. (https://discord.com/channels/280723930942013440/1141498209634623539) This improves visual quality of life.