validate plugin in CI

using https://github.com/Tracktion/pluginval

.github/workflows/build.yml

@@ -92,6 +92,35 @@ jobs:
             cargo xtask bundle "${package_args[@]}" --release
           fi
 
+      - name: Install pluginval
+        run: |
+          runner_name=${{ matrix.name }}
+          if [[ $runner_name = 'macos-universal' ]]; then
+            curl -L "https://github.com/Tracktion/pluginval/releases/latest/download/pluginval_macOS.zip" -o pluginval.zip; unzip pluginval
+          else
+          if [[ $runner_name = 'ubuntu-20.04' ]]; then
+            curl -L "https://github.com/Tracktion/pluginval/releases/latest/download/pluginval_Linux.zip" -o pluginval.zip; unzip pluginval
+          else
+          if [[ $runner_name = 'windows' ]]; then
+            powershell -Command "[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; Invoke-WebRequest https://github.com/Tracktion/pluginval/releases/latest/download/pluginval_Windows.zip -OutFile pluginval.zip"
+            powershell -Command "Expand-Archive pluginval.zip -DestinationPath ."
+          fi
+
+
+      - name: Validate VST3 plugin
+        run: |
+          runner_name=${{ matrix.name }}
+          if [[ $runner_name = 'macos-universal' ]]; then
+            pluginval.app/Contents/MacOS/pluginval --verbose --strictness-level 5 target/bundled/DEL2.vst3 || exit 1
+          else
+          if [[ $runner_name = 'ubuntu-20.04' ]]; then
+            ./pluginval --verbose --strictness-level 5 target/bundled/DEL2.vst3
+          else
+          if [[ $runner_name = 'windows' ]]; then
+            pluginval.exe --verbose --strictness-level 5 target/bundled/DEL2.vst3
+            if %ERRORLEVEL% neq 0 exit /b 1
+          fi
+
       - name: Determine build archive name
         run: |
           # Windows (usually) doesn't like colons in file names