add config usage

README.md

@@ -6,6 +6,18 @@ This script is intented to deploy for daily build chromium OS
 - copy common utility to {chromium}/src/scrips directory 
 
 # usage 
+## setup config.txt file
+```
+user_password=default
+working_dir=default
+repo_branch=default
+build_packages=true
+build_firmware=true
+build_image=true
+install_image=true
+dut_ip_addr=192.168.1.x
+```
+## execute command line
 ```
 # parameter is deprecated, please setup the user_passwork and repo_directory in config.txt
 $ ./main_cros_reposync_build.sh

config.txt

@@ -1,3 +1,8 @@
 user_password=default
 working_dir=default
-repo_branch=default
+repo_branch=default
+build_packages=true
+build_firmware=true
+build_image=true
+install_image=true
+dut_ip_addr=192.168.1.2