feat: add --dir option for the cli

[sunng87]

The dir option allows user to load all supported files from a directory.

There is also a minor refactoring to remove HandlerFactory from public API of the library. It's replaced by higher level api serve.

[Copilot]

Pull Request Overview

This PR introduces a new --dir option for the CLI to automatically register supported files in a specified directory as tables. In addition, it adjusts public re-exports in the library and updates the usage information in the README.

• Introduces a new method to include directory files by reading file extensions and adding them to corresponding table lists.
• Adjusts public API usage in the library and updates CLI arguments including new flags for --dir and --host.
• Updates README documentation to reflect version changes and CLI usage.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
datafusion-postgres/src/lib.rs	Updates public re-exports and internal module use for HandlerFactory.
datafusion-postgres-cli/src/main.rs	Implements the directory file inclusion logic and updates CLI flags.
README.md	Adjusts version, command usage and help text to reflect new options.

Comments suppressed due to low confidence (1)

datafusion-postgres/src/lib.rs:13

• [nitpick] The public re-export for HandlerFactory has been removed; if this change is intentional to encapsulate implementation details, consider adding a comment or documentation to clarify the rationale.

use handlers::HandlerFactory;