Add GitHub Actions workflow for NuGet publishing (#3)

Introduces a workflow to build, test, pack, and publish NuGet packages on pushes to main or via manual dispatch. Supports version override and handles API key securely for publishing to nuget.org.
Adds symbol package creation and conditional push to the publish workflow. Ensures .snupkg files are only pushed if present, and refines version extraction logic for robustness.

Author: KrastyTC

.github/workflows/publish.yml

@@ -0,0 +1,62 @@
+name: publish-nuget
+
+on:
+  push:
+    branches: [ main ]     
+  workflow_dispatch: 
+    inputs:
+      version:
+        description: 'Override version (optional, e.g. 0.1.2)'
+        required: false
+        type: string
+
+jobs:
+  pack-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Restore
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build -c Release
+
+      - name: Test
+        run: dotnet test -c Release --logger trx
+
+      - name: Resolve version
+        id: ver
+        shell: bash
+        run: |
+          if [ -n "${{ github.event.inputs.version }}" ]; then
+            PKGVER="${{ github.event.inputs.version }}"
+          else
+            FILE=$(git ls-files '*.csproj' | head -n1)
+            PKGVER=$(grep -oPm1 '(?<=<Version>)[^<]+' "$FILE" || true)
+            if [ -z "$PKGVER" ]; then echo "Version not found in $FILE"; exit 1; fi
+          fi
+          echo "PKGVER=$PKGVER" >> $GITHUB_ENV
+          echo "Using version: $PKGVER"
+
+
+      - name: Pack
+        run: dotnet pack -c Release -p:Version=${PKGVER} -o ./artifacts -p:IncludeSymbols=true -p:SymbolPackageFormat=snupkg
+
+      - name: Push to nuget.org
+        env:
+          NUGET_API_KEY: ${{ secrets.NUGET_API_KEY }}
+        run: |
+          if [ -z "$NUGET_API_KEY" ]; then
+            echo "NUGET_API_KEY secret is not set."; exit 1
+          fi
+          dotnet nuget push "./artifacts/*.nupkg"  --skip-duplicate --api-key "$NUGET_API_KEY" --source https://api.nuget.org/v3/index.json
+          if ls ./artifacts/*.snupkg 1> /dev/null 2>&1; then
+            dotnet nuget push "./artifacts/*.snupkg" --skip-duplicate --api-key "$NUGET_API_KEY" --source https://api.nuget.org/v3/index.json
+          else
+            echo "No symbol packages (.snupkg) found to push."
+          fi