Clarify the steps necessary to use the standalone QtMSBuild in CI/CD settings e.g. Azure DevOps

Suppose that a user uses Qt VS Tools to create a Qt/MSBuild project. They want to be able to upload this project to their build server using Azure DevOps and get the server to build the project (without opening the Visual Studio IDE's GUI).

Currently, even if the user manually installs https://download.qt.io/official_releases/vsaddin/3.2.0/qt-vsaddin-msbuild-3.2.0-rev.47.zip to %LOCALAPPDATA\QtMsBuild and set the QTMSBUILD environment variable to that folder, the build still fails with a "QtMsBuildNotFound" error. There also needs to be a way for MSBuild to resolve the "QtInstall" value from the *.vcxproj file.

Other tools have Custom tasks that can be selected for configuration in a YAML file; it would be great for Qt VS Tools to support something similar:

• https://learn.microsoft.com/en-us/azure/devops/pipelines/create-first-pipeline
• https://learn.microsoft.com/en-us/azure/devops/pipelines/get-started/yaml-pipeline-editor