Add module docstring to colors module

[Mohamed-Elwasila]

Summary

Adds a module-level docstring to typer/colors.py to document its purpose and usage.

Changes

• Added module docstring explaining color constants for terminal styling
• Included usage examples with typer.style() and typer.secho()

The colors module previously only had a comment. This adds proper documentation that will show up in IDE tooltips and generated docs.

[derOtto]

Hi @Mohamed-Elwasila,

thanks a lot for your contribution!

I'm not sure if this change really helps users when working with Typer.
There are already many different ways to print text with colors, and I was also confused myself about which colors I can use in which situation (using rich.print, typer.echo, typer.secho, typer.style).

Because of that, would it maybe be better to improve the documentation here: https://typer.tiangolo.com/tutorial/printing/
For example, by explaining more clearly how and which colors can be used for each of the different printing options?

I found these links for the two approaches:

• For Rich: https://rich.readthedocs.io/en/stable/appendix/colors.html
• For typer.echo, typer.secho, typer.style: https://click.palletsprojects.com/en/stable/api/#click.style