update to use QT6 to work in OBS version 28

OBS updated to version 28 in Sept 2022.

[https://github.com/obsproject/obs-studio/releases/tag/28.0.0](https://github.com/obsproject/obs-studio/releases/tag/28.0.0)
> As of May 2020, version 5 of the Qt user interface toolkit ceased public development and is no longer being updated. Since then, our need for a more up-to-date version has been increasing as time goes by. With version 28.0, we felt it was important for us to update our user interface toolkit to the latest version; not just to gain access to the latest features, but also for the latest bug fixes and improved support for newer operating systems and architectures such as Windows 11 and Apple Silicon. Unfortunately, this also means that certain plugins that depend on version 5 of Qt will no longer work when you upgrade to version 28.0 and will need to be updated.

So, it need to update src files and build instructions

Start by reviewing the source files under src and the project’s build instructions, then compare their current Qt assumptions with OBS version 28 and its Qt 6 migration notes. Done means the source and build instructions consistently support the OBS 28 environment and the project can be built successfully against it.

Written by the indexing model from the issue text.