apps: resnet18: Add README for development

Signed-off-by: xychen <xychen@listenai.com>
1 job 于feat/resnet18 in 2 minute 和 4 second (queued for 1 second)
状态 作业 ID 名称 覆盖率
  Ztest
已通过 #60889
zgsz-03 generic
ztest_build_only

00:02:04