Update .gitignore to exclude NuGet packages, tools, and PowerShell DLLs

.gitignore

@@ -35,6 +35,16 @@ ScaffoldingReadMe.txt
 *.nupkg
 # NuGet Symbol Packages
 *.snupkg
+# The packages folder can be ignored because of Package Restore
+**/[Pp]ackages/*
+# except build/, which is used as an MSBuild target.
+!**/[Pp]ackages/build/
+
+# NuGet tools
+nuget.exe
+
+# DLLs in PowerShell directory (these should be built, not committed)
+PowerShell/*.dll
 
 # Others
 ~$*