cmd/relui: add package comment

Copy the description of relui to a package comment.
Adjust README formatting so the header shows up as expected.

For golang/go#40279.

Change-Id: I74b9ee7ff67c94c885aea5231393928e8b5be647
Reviewed-on: https://go-review.googlesource.com/c/build/+/245645
Reviewed-by: Alexander Rakoczy <alex@golang.org>
diff --git a/cmd/relui/README.md b/cmd/relui/README.md
index eb1b511..0f5d73e 100644
--- a/cmd/relui/README.md
+++ b/cmd/relui/README.md
@@ -1,4 +1,4 @@
-#golang.org/x/build/cmd/relui
+# golang.org/x/build/cmd/relui
 
 ```
                ▀▀█             ▀
@@ -9,4 +9,3 @@
 ```
 
 relui is a web interface for managing the release process of Go.
-
diff --git a/cmd/relui/main.go b/cmd/relui/main.go
index 9c1587f..fced950 100644
--- a/cmd/relui/main.go
+++ b/cmd/relui/main.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// relui is a web interface for managing the release process of Go.
 package main
 
 import (
diff --git a/cmd/relui/protos/protos.go b/cmd/relui/protos/protos.go
index 9e4bded..295e877 100644
--- a/cmd/relui/protos/protos.go
+++ b/cmd/relui/protos/protos.go
@@ -1,6 +1,7 @@
 // Copyright 2020 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
+
 package protos
 
 // Run "go generate" in this directory to update. You need to have: