Add Github Actions for Windows (#24504)

Setup Installer CI (#25184), (#25191)

Co-authored-by: Zack Galbreath <zack.galbreath@kitware.com>
Co-authored-by: lou.lawrence@kitware.com <lou.lawrence@kitware.com>
Co-authored-by: Betsy McPhail <betsy.mcphail@kitware.com>

.github/workflows/setup_git.ps1

@@ -0,0 +1,16 @@
+# (c) 2021 Lawrence Livermore National Laboratory
+
+Set-Location spack
+
+git config --global user.email "spack@example.com"
+git config --global user.name "Test User"
+
+if ($(git branch --show-current) -ne "develop")
+{
+    git branch develop origin/develop
+}
+
+if ($(git branch --show-current) -ne "features/windows-support")
+{
+    git branch features/windows-support origin/features/windows-support
+}