Add support for InstallScripts

[EdgarMagalhaes]

Reason

InstallScripts are useful for setting up environment variables, running processes during installation, and cleaning up files upon uninstallation, thereby enhancing the overall user experience.

Changes

• Adds support for InstallScripts

InstallScripts can now be optionally configured by setting the depot[id]InstallScriptPath variable.

Example

jobs:
  deployToSteam:
    runs-on: ubuntu-latest
    steps:
      - uses: game-ci/steam-deploy@v3
        with:
          username: ${{ secrets.STEAM_USERNAME }}          
          configVdf: ${{ secrets.STEAM_CONFIG_VDF}}          
          appId: 1234560
          buildDescription: v1.2.3
          rootPath: build
          depot1Path: StandaloneWindows64
          depot1InstallScriptPath: StandaloneWindows64/install_script.vdf
          depot2Path: StandaloneLinux64
          releaseBranch: prerelease

Checklist

• Read the contribution guide and accept the code of conduct
• Readme (updated or not needed)
• Tests (added, updated or not needed)

[GabLeRoux]

This looks good to me. Should we update this page as well?
https://game.ci/docs/github/deployment/steam

[EdgarMagalhaes]

Sure, I'll create a PR on https://github.com/game-ci/documentation

[EdgarMagalhaes]

Documentation PR available at game-ci/documentation#467