Add watchdog dependency.

setup.cfg

@@ -51,6 +51,7 @@ install_requires =
     typer[all]
     urllib3>=1.26.18
     uvicorn[standard]
+    watchdog
 # The usage of test_requires is discouraged, see `Dependency Management` docs
 # tests_require = pytest; pytest-cov
 # Require a specific Python version, e.g. Python 2.7 or >= 3.4