chore: silence dead_code warnings on Phase 2 stubs

Use #[expect(dead_code)] on stub fields that won't be used until
Phase 2. The compiler will warn when the expectation becomes
unnecessary.

Author: thomasnemer

crates/ie-html/src/tokenizer.rs

@@ -1,7 +1,9 @@
 use anyhow::Result;
 
 pub struct Tokenizer<'a> {
+    #[expect(dead_code)]
     input: &'a str,
+    #[expect(dead_code)]
     pos: usize,
 }
 

crates/ie-js/src/lib.rs

@@ -7,6 +7,7 @@ use anyhow::Result;
 use boa_engine::Context;
 
 pub struct JsRuntime {
+    #[expect(dead_code)]
     context: Context,
 }