[CI] Install libpng when on Windows & macOS

Author: dpt

.github/workflows/ci.yml

@@ -12,8 +12,8 @@ jobs:
       matrix:
         config:
           - { name: "Ubuntu build",  os: "ubuntu-latest",  install: "sudo apt-get install cmake ninja-build libpng-dev" }
-          - { name: "Windows build", os: "windows-latest", install: "choco install cmake ninja pkgconfiglite" }
-          - { name: "macOS build",   os: "macos-latest",   install: "brew install cmake ninja" }
+          - { name: "Windows build", os: "windows-latest", install: "choco install cmake ninja libpng pkgconfiglite" }
+          - { name: "macOS build",   os: "macos-latest",   install: "brew install cmake ninja libpng pkgconf" }
     steps:
       - uses: actions/checkout@v4
       - run: ${{ matrix.config.install }}