update global git config code example

Example 1: git config global

$ git config --global user.name "John Doe"
$ git config --global user.email [email protected]

Example 2: list config git

git config --list

Example 3: git configure default editor

# Set Emacs as the default editor
$ git config --global core.editor emacs   
# Set Visual Studio Code as the default editor
$ git config --global core.editor code