automatically produce MSI files for releases

This commit:

- Adds config for building Windows installers
- Adds an action for fetching exe files built by goreleaser
- Adds an action for building Windows installers
- Adds an action for adding MSI files to an existing GH release
- Adds MSI signing to our release flow
- Disables homebrew formula bumping for prereleases
- Allows the release asset copying action to copy windows assets

sign.ps1

@@ -0,0 +1,13 @@
+param (
+    [string]$Certificate = $(throw "-Certificate is required."),
+    [string]$Executable = $(throw "-Executable is required.")
+)
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = "Stop"
+
+$thumbprint = "fb713a60a7fa79dfc03cb301ca05d4e8c1bdd431"
+$passwd = $env:GITHUB_CERT_PASSWORD
+$ProgramName = "GitHub CLI"
+
+& .\signtool.exe sign /d $ProgramName /f $Certificate /p $passwd /sha1 $thumbprint /fd sha256 /tr http://timestamp.digicert.com /td sha256 /v $Executable