doc: add Snowflake example and reorganize directory structure

examples/connect/snowflake/streamlit/README.md

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+# Streamlit Example
+
+## Start the app locally
+
+```bash
+SNOWFLAKE_ACCOUNT = "<snowflake-account-identifier>"
+SNOWFLAKE_WAREHOUSE = "<snowflake-warehouse-name>"
+
+# USER is only required when running the example locally with external browser auth
+SNOWFLAKE_USER="<snowflake-username>" streamlit run app.py
+```
+
+## Deploy to Posit Connect
+
+Validate that `rsconnect-python` is installed:
+
+```bash
+rsconnect version
+```
+
+Or install it as documented in the [installation](https://docs.posit.co/rsconnect-python/#installation) section of the documentation.
+
+To publish, make sure `CONNECT_SERVER`, `CONNECT_API_KEY`, `SNOWFLAKE_ACCOUNT`, `SNOWFLAKE_WAREHOUSE` have valid values. Then, on a terminal session, enter the following command:
+
+```bash
+rsconnect deploy streamlit . \
+  --server "${CONNECT_SERVER}" \
+  --api-key "${CONNECT_API_KEY}" \
+  --environment SNOWFLAKE_ACCOUNT \
+  --environment SNOWFLAKE_WAREHOUSE
+```
+
+Note that the Snowflake environment variables do not need to be resolved by the shell, so they do not include the `$` prefix.
+
+The Snowflake environment variables only need to be set once, unless a change needs to be made. If the values have not changed, you don’t need to provide them again when you publish updates to the document.
+
+```bash
+rsconnect deploy streamlit . \
+  --server "${CONNECT_SERVER}" \
+  --api-key "${CONNECT_API_KEY}"
+```

examples/connect/snowflake/streamlit/app.py

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+# -*- coding: utf-8 -*-
+# mypy: ignore-errors
+import os
+
+import pandas as pd
+import streamlit as st
+import snowflake.connector
+
+from posit.connect.external.snowflake import PositAuthenticator
+
+ACCOUNT = os.getenv("SNOWFLAKE_ACCOUNT")
+WAREHOUSE = os.getenv("SNOWFLAKE_WAREHOUSE")
+
+# USER is only required when running the example locally with external browser auth
+USER = os.getenv("SNOWFLAKE_USER")
+
+# https://docs.snowflake.com/en/user-guide/sample-data-using
+DATABASE = os.getenv("SNOWFLAKE_DATABASE", "snowflake_sample_data")
+SCHEMA = os.getenv("SNOWFLAKE_SCHEMA", "tpch_sf1")
+TABLE = os.getenv("SNOWFLAKE_TABLE", "lineitem")
+
+session_token = st.context.headers.get("Posit-Connect-User-Session-Token")
+auth = PositAuthenticator(
+    local_authenticator="EXTERNALBROWSER",
+    user_session_token=session_token)
+
+con = snowflake.connector.connect(
+    user=USER,
+    account=ACCOUNT,
+    warehouse=WAREHOUSE,
+    database=DATABASE,
+    schema=SCHEMA,
+    authenticator=auth.authenticator(),
+    token=auth.token(),
+)
+
+snowflake_user = con.cursor().execute("SELECT CURRENT_USER()").fetchone()
+st.write(f"Hello, {snowflake_user[0]}!")
+
+with st.spinner("Loading data from Snowflake..."):
+    df = pd.read_sql_query(f"SELECT * FROM {TABLE} LIMIT 10", con)
+
+st.dataframe(df)

examples/connect/snowflake/streamlit/requirements.txt

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+snowflake-connector-python==3.12.1
+streamlit==1.37.0
+posit-sdk>=0.4.1