script: Add message to SyntaxError (#39056)

Adding an optional message to be attached to a SyntaxError. Unblocks
#39050.

The enum definition of Syntax is now `Syntax(Option<String>)`. Future
PRs should probably add more appropriate messages to some of the
`Syntax(None)`s.

Testing: Just a refactor
Fixes: Partially #39053

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>

components/script/dom/worklet.rs

@@ -143,7 +143,7 @@ impl WorkletMethods<crate::DomTypeHolder> for Worklet {
             Err(err) => {
                 // Step 4.
                 debug!("URL {:?} parse error {:?}.", module_url.0, err);
-                promise.reject_error(Error::Syntax, can_gc);
+                promise.reject_error(Error::Syntax(None), can_gc);
                 return promise;
             },
         };