Add Compilation & Testing On Windows

[brianmichel]

Requirements

• [x] I have added test coverage for new or changed functionality
• [x] I have followed the repository's pull request submission guidelines
• [x] I have validated my changes against all supported platform versions

Related issues

I didn't see any related issues.

Describe the solution you've provided

This enables the ability to compile this library on Windows environments that are using Swift. I've chosen to use the recent 5.9 release as it should be a good candidate to base support on for this library. We can probably go older, but I thought we'd start at the most recent release.

Describe alternatives you've considered

N/A

Additional context

I saw that Circle CI is being used, however I don't know of a clean way to install Swift in a Circle CI instance (could probably figure this out), but to ensure that there was some CI running and testing the Windows platform I've added a quick GitHub Action workflow that should also run and provide testing output.

[brianmichel]

It seems that the contract tests are broken on main as well as the other open PR (https://github.com/launchdarkly/swift-eventsource/pull/67) so I believe that breakage is unrelated to this PR. Clicking into the Circle CI build I see that tests do in fact still pass for all platforms (outside of the contract tests)

[keelerm84]

Good morning, and my apologies for not responding sooner!

I want you to know I will try to look at this PR soon and see about getting it merged in. I have some other work I have to attend to this iteration, but I have added a ticket to come back to this early next week.

Tracking internally as sc-218506.

[brianmichel]

Thanks @keelerm84!

[keelerm84]

@brianmichel just wanted to let you know I haven't forgotten about this. I had some last minute priority shifts which are going to take my attention for a bit.

[keelerm84]

Sorry this took so long to review and get resolved. Thank you for your contribution!