refactor: combine open launch args (#364)

Combine the `--open` and `-o` launch arguments into a single argument option.

tagstudio/tag_studio.py

@@ -17,14 +17,9 @@ def main():
 
     # Parse arguments.
     parser = argparse.ArgumentParser()
-    parser.add_argument(
-        "--open",
-        dest="open",
-        type=str,
-        help="Path to a TagStudio Library folder to open on start.",
-    )
     parser.add_argument(
         "-o",
+        "--open",
         dest="open",
         type=str,
         help="Path to a TagStudio Library folder to open on start.",