Update min node version to 16.6.0 (#957)

pynecone/constants.py

@@ -15,7 +15,7 @@ PACKAGE_NAME = "pynecone"
 # The current version of Pynecone.
 VERSION = pkg_resources.get_distribution(PACKAGE_NAME).version
 # Minimum version of Node.js required to run Pynecone.
-MIN_NODE_VERSION = "12.22.0"
+MIN_NODE_VERSION = "16.6.0"
 
 # Valid bun versions.
 MIN_BUN_VERSION = "0.5.8"