Globally ignore `.env` file

It is a common practice to store environment variables in a .env file in
development. This file is read by tools such as foreman and dotenv. This
file can contain sensitive information such as secret keys and should
always be excluded from version control
Add Git credentials.
Initialise rbenv on startup.
Add Homebrew directory to PATH.
Move personal details to local files.
Add Github Enterprise settings.
Add Github CLI.
Look for GitHub Enterprise settings.