doc: Add release instructions

We need release instructions to use them as a check-list at release
creation time.

Signed-off-by: Stanislav Bogatyrev <stanislav@nspcc.ru>

doc/release_instructions.md

@@ -0,0 +1,53 @@
+# Release instructions
+
+This documents outlines the neofs-api release process, and can be used as a TODO
+list for a new release.
+
+## Pre-release checks
+
+These should run successfully:
+* `make lint`
+
+## Pre-release actions
+
+These must be run:
+* `make doc`
+
+## Writing CHANGELOG
+
+Add an entry to the CHANGELOG.md following the style established there.
+
+Add a codename for releases with new major version, version and release date in
+the heading. Write a paragraph describing the most significant changes done in
+this release. Then add sections with what was added, changed and removed,
+describing each change briefly with a reference to GitHub issues, where
+available.
+
+## Tag the release
+
+Use `vX.Y.Z` tag following the semantic versioning standard. For pre-release
+versions use `vX.Y.Z-rc.N` scheme.
+
+## 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 v2.7.0
+```
+
+## Make a proper Github release
+
+Edit an automatically-created release on Github.
+
+Release title has to follow `<version> <Romanized codename> (<Hangeul, Hanja
+codename> )` scheme for major releases and just `<version>` for regular point
+releases.
+
+## Post-release actions
+
+* Close corresponding X.Y.Z Github milestone
+* Make announcements in Matrix and Discord channels
+* Update [NeoFS Technical Specification](https://github.com/nspcc-dev/neofs-spec)