fixed dependencies

vendor/github.com/go-pdf/fpdf/wbuf.go

@@ -0,0 +1,17 @@
+// Copyright ©2021 The go-pdf Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package fpdf
+
+type wbuffer struct {
+	p []byte
+	c int
+}
+
+func (w *wbuffer) u8(v uint8) {
+	w.p[w.c] = v
+	w.c++
+}
+
+func (w *wbuffer) bytes() []byte { return w.p }