feat(loaders): CSV Loader to Document Loaders

[Tachikoma000]

This PR implements a CSV loader as part of the document loaders module in Rig. It allows users to easily load and process CSV documents for use in RAG systems and other document processing tasks.

Changes

• Implemented CsvLoader struct in src/document_loaders/csv.rs
• Added CsvLoader to the document_loaders module
• Implemented DocumentLoader trait for CsvLoader
• Used the csv crate for CSV parsing
• Added error handling for file operations and CSV parsing
• Updated Cargo.toml with the csv dependency
• Updated documentation with CsvLoader usage examples

Implementation Details The CsvLoader uses the csv crate to parse CSV files and extract content. It handles potential errors such as file not found or parsing errors. The extracted content is converted into a single DocumentEmbeddings object for further processing in Rig. Each row of the CSV is formatted as "header: value" pairs, separated by newlines.

Testing Ran tests to ensure the CsvLoader correctly loads CSV files and handles various edge cases. The tests covered:

• Loading a valid CSV file
• Handling a non-existent file
• Processing a CSV with multiple columns and rows
• Dealing with empty CSV files
• Handling CSV files with different delimiters

Documentation Code files are commented, and usage examples have been added to the documentation.

Related Issue Closes #29

Checklist

• [x] Code follows the project's coding style
• [x] Tests have been added and all tests pass
• [x] Documentation has been updated
• [x] Commit messages are clear and descriptive
• [x] Changes have been reviewed for potential performance impacts

Additional Notes This implementation focuses on converting CSV data into a single document for embedding. Future enhancements could include options for creating separate embeddings for each row or handling more complex CSV structures.

[cvauclair]

This is being (re-)implemented in #55