feat: Allow --export to default to 'accounts.txt' when no argument is provided

This commit modifies the `argparse` setup for the `--export` (-e) argument. By adding `nargs='?'` and `const='accounts.txt'`, the argument can now be used as a flag without requiring a subsequent file path. If the `-e` flag is present without a value, `accounts.txt` will be used as the default input file for export operations. The `default='accounts.txt'` remains to handle cases where the `-e` flag is not provided at all.

Author: FebraS

cli/parser.py

@@ -56,7 +56,9 @@ def setupArgParse():
 
     # Adding agrument --export or -e
     parser.add_argument('-e', '--export',
+                        nargs='?',
                         type=str,
+                        const='accounts.txt',
                         default='accounts.txt',
                         help='Specify the file to read account URIs from. Default is accounts.txt.')