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/worker.rs

@@ -179,7 +179,7 @@ impl WorkerMethods<crate::DomTypeHolder> for Worker {
         // Step 2-4.
         let worker_url = match global.api_base_url().join(&compliant_script_url) {
             Ok(url) => url,
-            Err(_) => return Err(Error::Syntax),
+            Err(_) => return Err(Error::Syntax(None)),
         };
 
         let (sender, receiver) = unbounded();