update readme and version etc

Author: Chenglong-MS

README.md

@@ -22,6 +22,14 @@ Transform data and create rich visualizations iteratively with AI 🪄. Try Data
 
 ## News 🔥🔥🔥
 
+- [04-23-2025] Data Formulator 0.2.1: External Data Loader 
+  - We introduced an external data loader to make import data easier. 
+    - Example data loaders from MySQL and Azure Data Explorer (Kusto) are provided.
+  - Call for action:
+    - Users: let us know which data source you'd like to load data from.
+    - Developers: help us build more data loaders.
+  - Created a discord channel for discussions.
+
 - [04-23-2025] Data Formulator 0.2: working with *large* data 📦📦📦
   - Explore large data by:
     1. Upload large data file to the local database (powered by [DuckDB](https://github.com/duckdb/duckdb)).

py-src/data_formulator/data_loader/README.md

@@ -0,0 +1,36 @@
+## Data Loader Module
+
+This module provides a framework for loading data from various external sources into DuckDB. It follows an abstract base class pattern to ensure consistent implementation across different data sources.
+
+### Building a New Data Loader
+
+The abstract class `ExternalDataLoader` defines the data loader interface. Each concrete implementation (e.g., `KustoDataLoader`, `MySQLDataLoader`) handles specific data source connections and data ingestion.
+
+To create a new data loader:
+
+1. Create a new class that inherits from `ExternalDataLoader`
+2. Implement the required abstract methods:
+   - `list_params()`: Define required connection parameters
+   - `__init__()`: Initialize connection to data source
+   - `list_tables()`: List available tables/views
+   - `ingest_data()`: Load data from source
+   - `view_query_sample()`: Preview query results
+   - `ingest_data_from_query()`: Load data from custom query
+3. Register the new class into `__init__.py` so that the front-end can automatically discover the new data loader.
+
+The UI automatically provide the query completion option to help user generate queries for the given data loader (from NL or partial queries).
+
+### Example Implementations
+
+- `KustoDataLoader`: Azure Data Explorer (Kusto) integration
+- `MySQLDataLoader`: MySQL database integration
+
+### Testing
+
+Ensure your implementation:
+- Handles connection errors gracefully
+- Properly sanitizes table names
+- Respects size limits for data ingestion
+- Returns consistent metadata format
+
+Launch the front-end and test the data loader.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "data_formulator"
-version = "0.2.1.1"
+version = "0.2.1.2"
 
 requires-python = ">=3.9"
 authors = [