Update release instructions

Author: electroly

CONTRIBUTING.md

@@ -57,6 +57,8 @@ In AWS, a `c5a.xlarge` instance running Windows Server 2022 will do.
 - Commit changes using commit message "Version X.X.X", and push.
 - Wait for GitHub Actions to build.
 - Test the zip and MSI in the GitHub Actions output. Rename them to `SQLNotebook-X.X.X.*`.
+- PowerShell: Set `$sha1` to the hash of the code signing certificate, then: `signtool sign /v /tr http://timestamp.sectigo.com /fd SHA256 /td SHA256 /sha1 $sha1 filename` for the `.msi`.
+- Unpack the `.zip`, sign `SqlNotebook.exe`, and repack it.
 - Create release on GitHub, upload zip and msi.
     - Let GitHub create a new tag, name it `vX.X.X`.
     - Set release title to `vX.X.X`.

ps1/New-Release.ps1

@@ -46,11 +46,6 @@ if (-not (Test-Path $wixDir)) {
     throw "WiX not found!"
 }
 
-$signtool = "C:\Program Files (x86)\Windows Kits\10\bin\$windowsSdkVersion\x64\signtool.exe"
-if (-not (Test-Path $signtool)) {
-    throw "Signtool not found!"
-}
-
 # Do the build
 Write-Output "Restoring source dependencies."
 & ps1\Update-Deps.ps1