chore: add NuGet packaging script and .gitignore for build

Introduces a PowerShell script to automate restoring, building, and packing the Wpf.Ui.Violeta project into NuGet packages. Also adds a .gitignore to exclude generated .nupkg and .snupkg files from version control.

Author: emako

build/.gitignore

@@ -0,0 +1,2 @@
+*.nupkg
+*.snupkg

build/nuget_pack.ps1

@@ -0,0 +1,16 @@
+Set-Location $PSScriptRoot
+
+$projects = @(
+    "..\src\Wpf.Ui.Violeta"
+)
+
+foreach ($proj in $projects) {
+    Push-Location $proj
+    Write-Host "Processing $proj..."
+    dotnet restore
+    dotnet build -c Release
+    dotnet pack -c Release -o ../../build/
+    Pop-Location
+}
+
+Pause