Add PRX/Stub Library Example/Guide

Dynamic Link is an essential part in PSP Programming. It's also the foundation of PSPSDK and CFW. However, current website doesn't include such guide on how to write export table, generate .S stub etc. One has to dive into Makefiles to figure out the complete process.

I'd like to add a guide to the current website that includes:

• How to build PRX for others to use

  • How to write C code for PRX program (module_start/module_stop)
  • How to write export table
  • How to use psp-build-exports -b to convert export table into C code
  • How to write correct Makefile (-nostartfiles flags etc)
  • How to generate .S file using psp-build-exports -k
  • How to generate .a Stub Library using psp-ar

• How to load PRX dynamically

  • System Calls such as sceKernelLoadModule, sceKernelFindModuleByUID, sceKernelStartModule (? Not quite familiar with this part)
  • What .S file does and how psp-fixup-imports works

• Other Topics

  • Kernel Module / User Module(?) Calling Constraints(?)

Looking forward to your suggestions!

首先调查当前网站以及 issue 要求读者检查的现有 Makefiles。研究围绕 psp-build-exports、psp-ar、psp-fixup-imports 和所列系统调用展开的 PRX 构建与动态加载工作流。完成的标准是网站包含一份连贯的指南，涵盖所要求的构建、加载、stub 库和模块约束主题。