LibJS: Add a Completion(ThrowCompletionOr<Value> const&) constructor

Author: https://github.com/linusg
Commit: 68ac13a192
Pull-request: https://github.com/SerenityOS/serenity/pull/10913
Reviewed-by: https://github.com/IdanHo ✅

Userland/Libraries/LibJS/Runtime/Completion.h

@@ -46,6 +46,8 @@ public:
             VERIFY(!m_value->is_empty());
     }
 
+    Completion(ThrowCompletionOr<Value> const&);
+
     // 5.2.3.1 Implicit Completion Values, https://tc39.es/ecma262/#sec-implicit-completion-values
     // Not `explicit` on purpose.
     Completion(Value value)