Add powershell example for 'git pr' alias (#1666)

Author: XChaitanyaX

getting-started/git-boot-camp.rst

@@ -462,12 +462,19 @@ Or set up a Git alias:
 
       git config --global alias.pr '!sh -c "git fetch upstream pull/${1}/head:pr_${1} && git switch pr_${1}" -'
 
-.. tab:: Windows
+.. tab:: Windows cmd
 
    .. code-block:: dosbatch
 
       git config --global alias.pr "!sh -c 'git fetch upstream pull/${1}/head:pr_${1} && git switch pr_${1}' -"
 
+.. tab:: Windows Powershell
+
+   .. code-block:: shell
+
+      git config --global alias.pr '!f() { git fetch upstream pull/$1/head:pr_$1 && git checkout pr_$1; }; f'
+
+
 The alias only needs to be done once.  After the alias is set up, you can get a
 local copy of a pull request as follows::