bytes: add ReplaceAll example

Change-Id: I36cc0b68a5a47ac78982b05118c58723c9c6648c
GitHub-Last-Rev: 0704d9569407d8b84d1ddcf845b759f7daa91ec1
GitHub-Pull-Request: golang/go#29203
Reviewed-on: https://go-review.googlesource.com/c/153842
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/bytes/example_test.go

@@ -298,6 +298,12 @@ func ExampleReplace() {
 	// moo moo moo
 }
 
+func ExampleReplaceAll() {
+	fmt.Printf("%s\n", bytes.ReplaceAll([]byte("oink oink oink"), []byte("oink"), []byte("moo")))
+	// Output:
+	// moo moo moo
+}
+
 func ExampleRunes() {
 	rs := bytes.Runes([]byte("go gopher"))
 	for _, r := range rs {