Add README with release instructions (#483)

* Add README with release instructions

* Mention update_remote_tools.sh

README.md

@@ -0,0 +1,15 @@
+# Bazel Mini Container Image Tools
+
+This repository contains the rust source code for the tools binaries used in
+[`rules_minidock`](https://github.com/bazeltools/rules_minidock).
+
+## Release process
+
+To cut a new release, use the
+[Releases](https://github.com/bazeltools/rules_minidock_tools/tags)
+UI to "Draft a new release" and hit the button to generate release notes.
+A new release will trigger GitHub actions to build the various binaries
+and attach them to the release.
+
+To pull a new tools release into `rules_minidock`, see that repo's
+[`update_remote_tools.sh`](https://github.com/bazeltools/rules_minidock/blob/main/minidock/remote_tools/update_remote_tools.sh).