refactor: move branch command to branch ls subcommand

src/git_flow/command/branch/__init__.py

@@ -0,0 +1,6 @@
+import typer
+
+from git_flow.command.branch import ls
+
+app = typer.Typer(name="branch")
+app.add_typer(ls.app)

src/git_flow/command/branch/ls.py

@@ -3,12 +3,12 @@ from typing import Annotated
 import typer
 from rich.console import Console
 
-import git_flow.command.base as base
 from git_flow import (
     TRASH_BRANCH_PREFIX,
     WIP_BRANCH_PREFIX,
     GitFlowError,
 )
+from git_flow.command import base
 from git_flow.git import Git
 
 BRANCH_FORMAT = "%(refname:short)"
@@ -18,7 +18,7 @@ console = Console()
 
 
 @app.command()
-def branch(
+def ls(
     environment: Annotated[
         str | None,
         typer.Argument(