Add nuget.exe back to vendor. We no longer need it, but it might be useful for others.

vendor/README.md

@@ -8,6 +8,11 @@ This folder contains pre-compiled binaries from a variety of sources. These shou
 - Can also be downloaded from NuGet, from here https://www.nuget.org/packages/Microsoft.NETCore.App.Host.win-x86/6.0.0
 - MIT License: https://github.com/dotnet/runtime/blob/main/LICENSE.TXT
 
+### nuget.exe
+- Used with the `pack` command to bundle an application directory into a nuget package, which is then used to create Squirrel releases
+- Can be found at https://www.nuget.org/downloads
+- Apache 2.0 License: https://github.com/NuGet/NuGet.Client/blob/dev/LICENSE.txt
+
 ### rcedit.exe
 - Updates PE resources, like VersionInfo or icons. It is used when generating `Setup.exe` and `Update.exe` to apply the user preferences.
 - Can be found at https://github.com/electron/rcedit/releases