move to api crate

xr_api/src/lib.rs

@@ -0,0 +1,12 @@
+pub mod api;
+pub mod api_traits;
+pub mod backend;
+pub mod error;
+pub mod types;
+
+pub mod prelude {
+    pub use super::api::*;
+    pub use super::api_traits::*;
+    pub use super::error::*;
+    pub use super::types::*;
+}