feat(cli): allow toggling JIT compilation

* Lune now accepts the `LUNE_LUAU_JIT` to toggle JIT compilation of Luau
  code.
* The `Runtime` struct exposes the `with_jit_enabled` method to library
  consumers.

crates/lune/src/cli/run.rs

@@ -1,4 +1,4 @@
-use std::process::ExitCode;
+use std::{env, process::ExitCode};
 
 use anyhow::{Context, Result};
 use clap::Parser;
@@ -43,6 +43,13 @@ impl RunCommand {
         // Create a new lune object with all globals & run the script
         let result = Runtime::new()
             .with_args(self.script_args)
+            // Enable JIT compilation unless it was requested to be disabled
+            .with_jit(
+                !matches!(
+                    env::var("LUNE_LUAU_JIT").ok(), 
+                    Some(jit_enabled) if jit_enabled == "0" || jit_enabled == "false" || jit_enabled == "off"
+                )
+            )
             .run(&script_display_name, strip_shebang(script_contents))
             .await;
         Ok(match result {

crates/lune/src/rt/runtime.rs

@@ -131,6 +131,15 @@ impl Runtime {
         self
     }
 
+    /**
+        Enables or disables JIT compilation.
+    */
+    #[must_use]
+    pub fn with_jit(self, enabled: bool) -> Self {
+        self.inner.lua().enable_jit(enabled);
+        self
+    }
+
     /**
         Runs a Lune script inside of the current runtime.