Only publish GitHub releases for main

Author: nblumhardt

ci/win-x64/build.ps1

@@ -27,7 +27,10 @@ Invoke-NuGetPack ($version)
 
 if ($env:CI_EVENT -eq "push" -and $env:NUGET_API_KEY -ne "") {
     Publish-NuPkg ($version)
-    Publish-GitHubRelease($version)
+    
+    if ($env:CI_TARGET_BRANCH -eq "main") {
+        Publish-GitHubRelease($version)
+    }
 }
 else {
     Write-Output "Not publishing NUPKG or GitHub release"