Let Rojo pull auth cookie from registry on Windows

src/auth_cookie.rs

@@ -0,0 +1,30 @@
+//! Implementation of automatically fetching authentication cookie from a Roblox
+//! Studio installation.
+
+#[cfg(windows)]
+pub fn get_auth_cookie() -> Option<String> {
+    use winreg::{enums::HKEY_CURRENT_USER, RegKey};
+
+    let hkcu = RegKey::predef(HKEY_CURRENT_USER);
+    let cookies = hkcu
+        .open_subkey("Software\\Roblox\\RobloxStudioBrowser\\roblox.com")
+        .ok()?;
+
+    let entry: String = cookies.get_value(".ROBLOSECURITY").ok()?;
+    let mut cookie = None;
+
+    for kv_pair in entry.split(",") {
+        let mut pieces = kv_pair.split("::");
+
+        if let Some("COOK") = pieces.next() {
+            cookie = pieces.next();
+        }
+    }
+
+    cookie.map(Into::into)
+}
+
+#[cfg(not(windows))]
+pub fn get_auth_cookie() -> Option<String> {
+    None
+}