feat(cmdeploy): read CHATMAIL_INI env var for default --config path

Avoids needing --config /etc/chatmail/chatmail.ini on every command
inside the Docker container, where CHATMAIL_INI is already set.

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -331,7 +331,7 @@ def add_config_option(parser):
         "--config",
         dest="inipath",
         action="store",
-        default=Path("chatmail.ini"),
+        default=Path(os.environ.get("CHATMAIL_INI", "chatmail.ini")),
         type=Path,
         help="path to the chatmail.ini file",
     )