Fixed an installation issue that misses some files

setup.py

@@ -12,7 +12,11 @@ setuptools.setup(
     long_description=long_description,
     long_description_content_type="text/markdown",
     url="https://github.com/Evan-Zhao/predictive-tuner",
-    packages=["predtuner"],
+    packages=setuptools.find_packages(),
+    package_data={
+        "predtuner.approxes": ["default_approx_params.json"]
+    },
+    include_package_data=True,
     install_requires=[
         "matplotlib>=3.3",
         "networkx>=2.5",