support python -m dpdata (#649)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced a new command-line interface for easier interaction with
the application.
- **Tests**
- Added tests to verify the correct version output from the new
command-line interface.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

dpdata/__main__.py

@@ -0,0 +1,4 @@
+from dpdata.cli import dpdata_cli
+
+if __name__ == "__main__":
+    dpdata_cli()

tests/test_cli.py

@@ -1,4 +1,5 @@
 import subprocess as sp
+import sys
 import unittest
 
 from context import dpdata
@@ -26,3 +27,12 @@ def setUpClass(cls) -> None:
     @classmethod
     def tearDownClass(cls) -> None:
         cls.system = None
+
+
+class TestClassScript(unittest.TestCase):
+    def test_class_script(self):
+        expected_version = dpdata.__version__
+        output = sp.check_output([sys.executable, "-m", "dpdata", "--version"]).decode(
+            "ascii"
+        )
+        assert output.splitlines()[0] == f"dpdata v{expected_version}"