component group fix (calling without a subcommand)

Author: RavinduWeerakoon

sdk/python/kfp/cli/component.py

@@ -357,9 +357,13 @@ def build_image(self, platform: str, push_image: bool):
             f'Built and pushed component container {self._target_image}')
 
 
-@click.group()
-def component():
+@click.group(invoke_without_command=True)
+@click.pass_context
+def component(ctx: click.Context):
     """Builds shareable, containerized components."""
+    if ctx.invoked_subcommand is None:
+        click.echo(ctx.get_help())
+        ctx.exit(0)
 
 
 @component.command()