添加pdf文件和镜像

开发笔记.md

@@ -44,7 +44,6 @@
     sudo apt-get install qemu-user-static live-build bison flex fakeroot cmake
     sudo apt-get install gcc-multilib g++-multilib unzip device-tree-compiler ncurses-dev libncurses5-dev
 
-
 6.泰山派sdk
     解压出来的.repo包执行下面命令
     .repo/repo/repo sync -l -j88