Update README file with build instructions.

python/README.md

@@ -45,3 +45,11 @@ def valid_date_udf(ts_column):
 # Create a Rule that uses the UDF to validate data
 valid_date_rule = Rule("valid_date_reading", valid_date_udf(F.col("reading_date")))
 ```
+
+## Building the project
+
+A Python `.whl` file can be generated by navigating to the `/python` directory and executing the following command :
+
+```bash
+$ python3 -m build
+```