Add setup.py to enable standard packaging and installation (pip/pipx/uv)

[Mys7ic]

Description

This PR adds a standard setup.py file to the repository.
Currently, users need to clone the repo and manage dependencies manually or set up aliases. By adding packaging metadata, the tools can be easily installed into isolated environments, with dependencies (impacket, ldap3, dnspython) resolved automatically.

This makes usage with modern tool managers like uv or pipx much smoother and exposes the scripts (e.g., krbrelayx.py, printerbug.py) directly to the PATH.

How to test / Install

1. Local Installation (Testing this PR)

You can test the installation directly from the source directory:

Using uv (Recommended):

uv tool install .
# Verify:
krbrelayx.py -h

Using pipx:

pipx install .

2. Remote Installation (After Merge)

Once merged, users can install the tools directly from GitHub without manual cloning:

Using uv:

uv tool install git+https://github.com/dirkjanm/krbrelayx

Using pipx:

pipx install git+https://github.com/dirkjanm/krbrelayx