Add CME Corn futures demo notebook

Barchart/README.md

@@ -0,0 +1,64 @@
+# Barchart utilities
+
+The `Barchart` package contains:
+
+- `BarchartHistoricalData`, a session-based client for Barchart historical
+  time-series responses.
+- `ContinuousFuturesBuilder`, which builds nearby futures series from explicit
+  contract data or a fetcher.
+
+## Install
+
+Install the runtime dependencies with:
+
+```powershell
+python -m pip install -r Barchart/requirements.txt
+```
+
+For the rendered Corn futures demo, install the optional notebook dependencies:
+
+```powershell
+python -m pip install -r Barchart/requirements-demo.txt
+```
+
+## Example
+
+```python
+from Barchart import BarchartFetcher, BarchartHistoricalData, ContinuousFuturesBuilder
+
+client = BarchartHistoricalData()
+fetcher = BarchartFetcher(client)
+builder = ContinuousFuturesBuilder(fetcher=fetcher, verbose=False)
+
+series = builder.build_from_root(
+    "KC",
+    line_number=1,
+    start="2024-01-01",
+    end="2024-12-31",
+)
+```
+
+## Corn futures demo
+
+Open `corn_futures_demo.ipynb` in Jupyter or VS Code. It uses CME/CBOT Corn
+futures (`ZC`) and demonstrates:
+
+- contract-level histories with realistic availability windows;
+- first and second nearby lines;
+- roll segments and nearby spreads; and
+- an optional live Barchart path controlled by `USE_LIVE_DATA`.
+
+The notebook runs on deterministic offline data by default, so it does not
+require credentials or a live network request to display the workflow.
+
+The client uses Barchart's web-session cookie handshake and endpoint, so it is
+subject to Barchart availability and any access terms that apply to your use
+of the service. No credentials are stored by this package.
+
+## Tests
+
+Run the Barchart tests with:
+
+```powershell
+python -m unittest discover -s Barchart/tests -v
+```