Add Windows support to the Curl backend

[JD557]

Before submitting pull request:

• Check if the project compiles by running sbt compile
• Verify docs compilation by running sbt compileDocs
• Check if tests pass by running sbt test (I had some issues with some tests, so I'll wait for the CI, but I did check that this worked locally on Windows with sn-vcpkg)
• Format code by running sbt scalafmt

On Windows, curl needs to be linked as libcurl instead of curl. On top of that, it requires crypt32.

I'm using a strategy similar to what Scala Native 0.5.0 uses to handle a similar problem with ZLib. See:

https://github.com/scala-native/scala-native/blob/12d57c527d241f6a1781ec9457492cdd6cc4a904/javalib/src/main/scala/scala/scalanative/ffi/zlib.scala#L8-L19

https://github.com/scala-native/scala-native/blob/main/javalib/src/main/scala/scala/scalanative/ffi/package.scala#L7

I was only able to test this on Windows, so please check if nothing is broken in Linux/MacOS.

[adamw]

Thank you!