Add document for Getting Started as an Application Designer

[GorgonMeducer]

In some resource-constrained systems, the Flash (ROM) and SRAM are limited (e.g. 64K Flash, 12K SRAM), or the memory space left for GUI applications is limited, so such systems cannot afford the cost of a decent GUI stack. Meanwhile, such a low-cost system usually won't have a complex graphical user interface, hence application developers can directly use the arm-2d APIs to draw the panels and scenes.

For those application designers, we need a dedicated Getting Started document.