Update code to support argument feature

Usage: python cpisign.py -k CPIKEY example1.json example2.json ...
and input the password of CPI key to sign the data

Change-Id: Ieb0183208aab351f907f41d69ec8052cce5cecb7
diff --git a/.gitignore b/.gitignore
index af3bea8..01c9c58 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0
 
 venv_cbrs
+output
 *.p12