fix: add documentation for many classes where it was missing

src/util/errors/NotFoundHttpError.ts

@@ -1,5 +1,7 @@
 import { HttpError } from './HttpError';
-
+/**
+ * An error thrown when no data was found for the requested identifier.
+ */
 export class NotFoundHttpError extends HttpError {
   public constructor(message?: string) {
     super(404, 'NotFoundHttpError', message);

src/util/errors/UnsupportedMediaTypeHttpError.ts

@@ -1,7 +1,10 @@
 import { HttpError } from './HttpError';
 
+/**
+ * An error thrown when the media type of incoming data is not supported by a parser.
+ */
 export class UnsupportedMediaTypeHttpError extends HttpError {
   public constructor(message?: string) {
-    super(415, 'UnsupportedHttpError', message);
+    super(415, 'UnsupportedMediaTypeHttpError', message);
   }
 }