feat: Add pre-commit hook.

[augustebaum]

Closes #24.

Testing:

• Create a test_dir directory tracked by git containing only a pyproject.toml file respecting the poetry2conda requirements (i.e. that the [tool.poetry2conda] section have a name field).
• As described in the pre-commit docs, run

  cd /path/to/test_dir
  pre-commit try-repo /path/to/poetry2conda "poetry2conda" --all-files --verbose

The output should look something like:

===============================================================================
Using config:
===============================================================================
repos:
-   repo: /path/to/poetry2conda
    rev: f857af95a3e1c88492ad252e44593ce78f8881d5
    hooks:
    -   id: poetry2conda
===============================================================================
[INFO] Initializing environment for /path/to/poetry2conda.
[INFO] Installing environment for /path/to/poetry2conda.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
poetry2conda.............................................................Passed
- hook id: poetry2conda
- duration: 0.08s