Merge pull request #15164 from use-strict/patch-3

http-errors: Add missing constructor

http-errors/http-errors-tests.ts

@@ -83,3 +83,4 @@ var err = new createError.MisdirectedRequest();
 var err = new createError.MisdirectedRequest('Where should this go?');
 
 let error: createError.HttpError;
+console.log(error instanceof createError.HttpError);

http-errors/index.d.ts

@@ -23,6 +23,8 @@ declare module 'http-errors' {
             [code: string]: new (msg?: string) => HttpError;
 
             (...args: Array<Error | string | number | Object>): HttpError;
+            
+            HttpError: HttpErrorConstructor;
 
             Continue: HttpErrorConstructor;
             SwitchingProtocols: HttpErrorConstructor;