Add release instruction document

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

docs/release-instruction.md

@@ -0,0 +1,56 @@
+# Release instructions
+
+## Pre-release checks
+
+These should run successfully:
+ * build,
+ * unit-tests,
+ * integration tests in 
+ [neofs-devenv](https://github.com/nspcc-dev/neofs-devenv).
+
+## Writing changelog
+
+Add an entry to the `CHANGELOG.md` following the style established there. Add an 
+optional codename, version and release date in the heading. Write a paragraph
+describing the most significant changes done in this release. Add
+`Fixed`, `Added`, `Removed` and `Updated` sections with fixed bug descriptions
+and changes. Describe each change in detail with a reference to github issues if
+possible. 
+
+## Tag the release
+
+Use `vX.Y.Z` tag for releases and `vX.Y.Z-rc.N` for release candidates
+following the [semantic versioning](https://semver.org/) standard.
+
+## Push changes and release tag to github
+
+This step should bypass the default PR mechanism to get a correct result (so
+that releasing requires admin privileges for the project), both the `master`
+branch update and tag must be pushed simultaneously like this:
+
+    $ git push origin master v0.12.0
+
+## Prepare and push images to a dockerhub
+
+Create images for `neofs-storage`, `neofs-ir` and `neofs-cli` applications
+and push them into dockerhub (so that releasing requires privileges in nspccdev
+organization in dockerhub)
+
+    $ make images
+    $ docker push nspccdev/neofs-storage:0.12.0
+    $ docker push nspccdev/neofs-ir:0.12.0
+    $ docker push nspccdev/neofs-cli:0.12.0
+
+## Make a proper github release
+
+Edit an automatically-created release on github, copy things from changelog. 
+Make a release.
+
+## Close github milestone
+
+Close corresponding vX.Y.Z github milestone.
+
+## Post-release
+
+Prepare pull-request for 
+[neofs-devenv](https://github.com/nspcc-dev/neofs-devenv).