ci: add Dockerfile and README for CI image setup

Signed-off-by: Nandini Matam <nandini.matam@oss.qualcomm.com>

Author: nandini-matam

CI/README.md

@@ -1,7 +1,7 @@
 # kmake-image-packager
 
-Minimal Docker image for packaging bootable kernel artifacts
+Docker image for packaging bootable kernel artifacts
 
 **Outputs:** `efi.bin`, `dtb.img`, `boot.img`  
 
-This project focuses on generating bootable images from prebuilt kernel artifacts; if you already have a compiled kernel, a DTB, and an optional ramdisk, this container helps you quickly generate them.
+This project focuses on generating bootable images from prebuilt kernel artifacts(kernel image and DTB) with an optional ramdisk.