remove usage of metacall::switch and some edits in Rust docs

source/ports/rs_port/README.md

@@ -26,11 +26,11 @@ export function sum(a: number, b: number): number {
 
 `main.rs`
 ``` rust
-use metacall::{switch, metacall, loaders};
+use metacall::{initialize, metacall, load};
 
 fn main() {
     // Initialize MetaCall at the top
-    let _metacall = switch::initialize().unwrap();
+    let _metacall = initialize().unwrap();
 
     // Load the file
     load::from_single_file("ts", "sum.ts").unwrap();

source/ports/rs_port/src/lib.rs

@@ -41,11 +41,11 @@
 //! Now let's jump into Rust:
 //!
 //! ```
-//! use metacall::{switch, metacall, loaders};
+//! use metacall::{initialize, metacall, load};
 //!
 //! fn main() {
 //!     // Initialize MetaCall at the top
-//!     let _metacall = switch::initialize().unwrap();
+//!     let _metacall = initialize().unwrap();
 //!     
 //!     // Load the file (Checkout the loaders module for loading multiple files
 //!     // or loading from string)