Add direnv artifacts to gitignore

[den-is]

Checklist:

• I have read the Contributing guidelines.

Adds .envrc and .direnv to .gitignore.

These two files/dirs by purpose are similar to what already exists in the project's gitignore: venv, .venv, etc.
I manage my python environments using pyenv+direnv
.envrc usually has line that defines python environment for a specific directory/project:
layout pyenv miniconda3-3.11-23.10.0-1

That setting automatically creates .direnv directory similar to venv/.venv with Python environment.

Of course, it is better to ignore this operational files.