Add environment.txt to .gitignore to prevent accidental API key exposure

[Inengs]

environment.txt contains sensitive credentials including GitHub and GitLab API keys, RabbitMQ credentials, and database passwords. It is currently not listed in .gitignore, which means contributors could accidentally push it to GitHub and expose their credentials.

Other similar files like env.txt, docker_env.txt, and pyenv.txt are already in .gitignore. Adding environment.txt to .gitignore would be consistent with that pattern and prevent accidental exposure of sensitive information.

This was noticed while setting up locally using docker

Suggested fix:
Add environment.txt to .gitignore.