I made a pull request to address this issue as my first contribution to this project.

#46

Let me know if you have any suggestions or comments.

@gagb

Issue Title: Improve Basic CLI Help Text for markitdown
Description:
The markitdown tool installs and runs successfully when installed via pipx. However, when executing the command with --help or without any arguments, the output is unclear or does not provide sufficient guidance to new users.

Steps to Reproduce:
Install markitdown via pipx:
bash
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pipx install markitdown
Run the command without arguments:
bash
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markitdown
Alternatively, run the help command:
bash
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markitdown --help
Observed Behavior:
The output is either unclear, incomplete, or missing critical information about the tool's usage.
Expected Behavior:
The help text should clearly describe:
What the tool does.
How to use it (e.g., syntax and examples).
List of available commands and options.
Proposed Solution:
Update the CLI help text to provide:
A brief description of the tool.
A usage guide, including the command structure.
Examples of common use cases.
Example Help Text:

bash
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markitdown: A CLI tool for converting markdown files to HTML.

Usage:
markitdown [OPTIONS] <input_file.md> [output_file.html]

Options:
--help Show this help message and exit.
--version Display the current version of markitdown.

Examples:
markitdown input.md output.html
markitdown input.md

Additional Notes:
Contributors may need to explore the CLI parsing library used (e.g., argparse, click, etc.) to make the necessary improvements.
Ensure the updated help text aligns with any additional features or options provided by markitdown.