cmd/releaseschedule: basic doc and README.md

"cmd/releaseschedule" had no docs and no direction on what to do with the output. Would be better to have links to the wiki page and basic information on what to do with the output. Helps with discoverability as well if someone searches for information that SVG.

Add package doc with request to update wiki & links to wiki. Generate README.md with update-readmes.go.

Fixes golang/go#59314

Change-Id: I35713392624d36309b9f59a8f2e4b05ae5d0d8d7
GitHub-Last-Rev: ad4058b
GitHub-Pull-Request: #64
Reviewed-on: https://go-review.googlesource.com/c/build/+/480975
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Heschi Kreinick <heschi@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Heschi Kreinick <heschi@google.com>

cmd/releaseschedule/README.md

@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/cmd/releaseschedule.svg)](https://pkg.go.dev/golang.org/x/build/cmd/releaseschedule)
+
+# golang.org/x/build/cmd/releaseschedule
+
+Releaseschedule generates the release schedule diagram used on the release schedule wiki.

cmd/releaseschedule/main.go

@@ -1,3 +1,11 @@
+// Releaseschedule generates the release schedule diagram used
+// on the release schedule wiki.
+//
+// When this program is updated, regenerate the SVG and replace the old version
+// on the Go Release Cycle wiki page
+//
+// https://go.dev/s/release
+// https://golang.org/wiki/Go-Release-Cycle
 package main
 
 import (