Add code sign of Windows installer

Windows installer will now get automatically signed using Diffblue
code sign certificate so that it will no longer appear as from
unknown publisher when installer is executed.
Windows package release action has 5 tasks added:
1. Setup code sign environment where path to signtool.exe is added
to GITHUB_PATH environmental variable and PFX certificate file
name is kept as "pfxcert" variable in GITHUB_ENV envronmental
variable.
2. Decoding Personal Information Exchange file (*.pfx) from Github
Secrets into a file.
3. Signing the Windows Installer package with decoded certificate
using signtool from Windows SDK.
4. Deleting decoded certificate file.
5. Verifying the signature.

Author: piograb

.github/workflows/release-packages.yaml

@@ -112,6 +112,10 @@ jobs:
           choco install winflexbison3
       - uses: microsoft/setup-msbuild@v1.0.1
         name: Setup Visual Studio environment
+      - name: Setup code sign environment
+        run: | 
+          echo "$(Split-Path -Path $(Get-ChildItem -Path ${env:ProgramFiles(x86)} -Recurse -Filter 'signtool.exe' | Where-Object FullName -like '*10.0.19041.0\x64\signtool.exe').FullName)" >> $env:GITHUB_PATH
+          echo "pfxcert=$([string](Get-Location)+'\CodeSignCertificate.pfx')" >> $env:GITHUB_ENV
       - name: Configure with cmake
         run: |
           New-Item -ItemType Directory -Path build
@@ -130,6 +134,23 @@ jobs:
           $msi_name = Get-ChildItem -Filter *.msi -Name
           Write-Output "::set-output name=msi_installer::build/$msi_name"
           Write-Output "::set-output name=msi_name::$msi_name"
+      - name: Decode signing certificate
+        id: decode_certificate
+        run: |
+          $pfx_bytes=[System.Convert]::FromBase64String("${{ secrets.CODESIGNCERTPFX }}")
+          [IO.File]::WriteAllBytes($env:pfxcert, $pfx_bytes)
+      - name: Sign the installer
+        id: code_sign
+        run: |
+          & signtool.exe sign /f $env:pfxcert /p "${{ secrets.CODESIGNCERTPASSWORD }}" /tr http://tsa.starfieldtech.com ${{ steps.create_packages.outputs.msi_installer }}
+      - name: Remove signing certificate
+        id: remove_certificate
+        run: |
+          Remove-Item $env:pfxcert
+      - name: Verify installer signature
+        id: verify_codesign
+        run: |
+          & signtool.exe verify /pa ${{ steps.create_packages.outputs.msi_installer }}
       - name: Get release info
         id: get_release_info
         uses: bruceadams/get-release@v1.2.0