Update documentation

[yhong123]

Resolved #131

Summary
This PR updates and reorganises the Datafaker documentation to improve clarity, navigation, and onboarding for users. In particular, it adds a new tutorial covering the workflow required by Paul and Shipra for generating synthetic Camino data from Parquet files.

Changes

• Added "Tutorial: Generate Synthetic Data from CSV and Parquet" (tutorial_parquet.rst), which serves as the primary guide for Paul and Shipra's use case.
  • The existing DuckDB documentation (duckdb.rst) has been retained for the time being and can be removed later if Tim agrees that tutorial_parquet.rst provides sufficient coverage.
• Restructured the documentation into two main sections: "Getting Started" and "Advanced".
• Updated index.rst to:
  • Refresh the introduction.
  • Remove outdated notes.
  • Revise the table of contents to reflect the new documentation structure.
• Renamed "Quick Start" to "Command-line Interface (CLI) Guide" to better represent the scope and content of quickstart.rst.
  • This change can be reverted if the original title is preferred.
• Renamed "Introductory Tutorial" to "Tutorial: Generate Synthetic Data from PostgreSQL" to improve clarity and maintain consistency with the naming convention used for other tutorials.
• Corrected a minor formatting issue in installation.rst.
• Removed "Example: Loan Data" (loan_data.rst) from index.rst because the example describes Turing's SqlSynthGen rather than Datafaker.
  • The file itself remains in the repository and can be removed later if Tim agrees.
• Added requirements.txt file for building the Sphinx documentation.
  • The file specifies the versions of Sphinx and the Mermaid extension required to build the documentation.
  • This simplifies the process of creating a virtual environment and installing the necessary dependencies before running poetry run make html in the docs directory.
• Updated /datafaker/README.md to include a link to the documentation GitHub Pages site.

Future Work
The "Advanced" section would benefit from additional review and reorganisation. Further documentation improvements can be addressed in a subsequent documentation-focused PR.