Create CI target for `i686-pc-windows-msvc` on current windows

## Brief feature description

The platform is out of the box supported but some mistakes/bugs may occur when not using the right macro platform combination in c files.
See #235 where we needed to use `#if defined(_WIN32) || defined(_WIN64)`

Since the 32-bit platform is already tested fully, a simple single debug build on Windows should be sufficient.

Start by locating the repository's existing Windows CI configuration and the jobs that test platform targets. Add a single debug build for i686-pc-windows-msvc alongside the current Windows coverage. Done means the target builds successfully in CI and the existing Windows checks remain unchanged.

Written by the indexing model from the issue text.