LibCore: Add System::sleep_ms

Author: https://github.com/stasoid
Commit: a291a7f770
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2917
Reviewed-by: https://github.com/ADKaster ✅

Libraries/LibCore/System.cpp

@@ -1010,4 +1010,11 @@ bool is_socket(int fd)
     return !result.is_error() && S_ISSOCK(result.value().st_mode);
 }
 
+ErrorOr<void> sleep_ms(u32 milliseconds)
+{
+    if (usleep(1000 * milliseconds) != 0)
+        return Error::from_syscall("usleep"sv, -errno);
+    return {};
+}
+
 }