support Windows build

Unfortunately, the existing build and tests are based on Linux and this works well for Posix users (Mac, Unix, Linux, etc). Our CI only runs on ubuntu VMs. This can be said of basically all Pekko builds.

Windows users may or may not be able to build this project as is. We have no proof about this. Even if they could build it, some tests might fail.

Unfortunately, CI on Windows VMs can be time consuming to set up and in my experience can often be more brittle.

Windows users do have the choice to use https://en.wikipedia.org/wiki/Windows_Subsystem_for_Linux or to use solutions like dual boot, build VMs on Cloud Providers and Docker Containers.

Supporting Windows would be nice but we probably need Windows users to drive this.

Start by examining the existing Linux-based build and tests and the Ubuntu-only CI configuration. Investigate whether the project builds and its tests pass on Windows, then determine a reliable Windows CI approach. Done means Windows build and test support is demonstrated in CI.

Written by the indexing model from the issue text.