feat(file/stderr): RedirectStandardError stub for js (#305)

Add a 'file.RedirectStandardError()' stub for `GOOS=js` that panics if used.
The purpose is to allow code to compile under GOOS=js.

Author: andrewkroh

file/stderr_js.go

@@ -0,0 +1,30 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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:build js
+
+package file
+
+import (
+	"os"
+)
+
+// RedirectStandardError causes all standard error output to be directed to the
+// given file.
+func RedirectStandardError(toFile *os.File) error {
+	panic("RedirectStandardError not supported in js")
+}