docs: enhance '--miso' argument help description

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@ustc.edu.cn>

Author: njzjz

reacnetgenerator/commandline.py

@@ -52,7 +52,10 @@ def main_parser() -> argparse.ArgumentParser:
         ),
         action="store_true",
     )
-    parser.add_argument("--miso", help="Merge the isomers", type=int, default=0)
+    parser.add_argument("--miso", help=(
+        "Merge the isomers, and the highest frequency is used as the representative. 0, off; "
+        "1, merge the isomers with the same atoms and same bond-network but different bond orders; "
+        "2, merge the isomers with the same atoms with different bond networks."), type=int, default=0)
     parser_type = parser.add_mutually_exclusive_group()
     parser_type.add_argument(
         "--dump",