add support for pip install

[branchv]

This adds a pyproject.toml so users can pip install it. I've kept things the same as much as possible, but:

• I had to move the scripts under recon/ so pip can find and install them. I kept the existing scripts and just pointed them to the new location (note the PR diff doesn't track the rename but the individual commits do)
• I added a symlink recon/_version.py -> VERSION since setuptools needs to import the version from a python file

Demo:

$ python3.11 -m venv .venv
$ .venv/bin/pip install git+https://github.com/branchvincent/recon-ng@pyproject
$ .venv/bin/recon-cli --version
5.1.2