web-sys: add WorkerType feature

PR rustwasm#2656 added support settings `type` and `request_credentials` on
`WorkerOptions`. However, the `WorkerType` struct` was not exposed, as
the feature was not added to Cargo.toml.

crates/web-sys/Cargo.toml

@@ -1387,6 +1387,7 @@ WorkerGlobalScope = ["EventTarget"]
 WorkerLocation = []
 WorkerNavigator = []
 WorkerOptions = []
+WorkerType = []
 Worklet = []
 WorkletGlobalScope = []
 WorkletOptions = []