vendor dependencies, make some changes to how input is done

vendor/github.com/hajimehoshi/ebiten/v2/internal/png/generate.go

@@ -0,0 +1,21 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:generate go run gen.go
+
+// This package is a copy of the standard lib 'image/png' without registering
+// the decoder by image.RegisterFormat. Thus, users of this package don't
+// have to care about side-effect of registering format.
+
+package png