CI: enable multi-version builds on Windows (#335)
CI: enable multi-version builds on Windows (#335)

With the use of compnerd/gha-setup-swift, it is relatively easy to enable a
matrix build on Windows, enabling building and testing against different Swift
verisons.  Use this to enable builds for 5.5 and 5.6-dev.
jpsim/Yams,jpsim/Yams,jpsim/Yams