Add initial CI job for Windows target (#8088)

Clippy is disabled for now, due to many warnings in both `gpui` and
other code, see
https://github.com/zed-industries/zed/actions/runs/7980269779/job/21789529800
for more details.

Also, due to `#!/usr/bin/env bash` shebang in the `script/clippy`, it
starts in Windows CI with `shell: C:\Program Files\Git\bin\bash.EXE
-euxo pipefail {0}`

https://github.com/zed-industries/zed/actions/runs/7980269779/job/21789529800#step:4:3
It seems more appropriate to use PowerShell instead.

See `todo!("windows")` for all stubbed places currently.

Release Notes:

- N/A

crates/gpui/src/platform.rs

@@ -61,6 +61,10 @@ pub(crate) fn current_platform() -> Rc<dyn Platform> {
 pub(crate) fn current_platform() -> Rc<dyn Platform> {
     Rc::new(LinuxPlatform::new())
 }
+#[cfg(target_os = "windows")]
+pub(crate) fn current_platform() -> Rc<dyn Platform> {
+    todo!("windows")
+}
 
 pub(crate) trait Platform: 'static {
     fn background_executor(&self) -> BackgroundExecutor;