Add permission for using camera

The zxing library will need this permission to work
correctly.

app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest package="protect.card_locker"
           xmlns:android="http://schemas.android.com/apk/res/android">
 
+    <uses-permission
+        android:name="android.permission.CAMERA"/>
     <uses-permission
         android:maxSdkVersion="18"
         android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>