chore: update docs with a new release process

Author: Jorres

docs/README.md

@@ -1,16 +1,8 @@
 This document attempts to be some sort of a table of contents:
 
-## Operator release flow
 
-See [here](./release-flow.md).
+## Working on a feature
 
-## Writing and running tests
-
-See [here](./tests.md).
-
-## Storage
-
-#### [Storage state machine schema](./storage-state-machine-schema.md)
-
-This describes which states the Storage object has and in what order they are
-traversed.
+- don't forget to use `changie` to generate a changelog entry, whenever you complete a feature
+- see [here](./tests.md) to learn how to run tests
+- see [here](./tests.md) to learn how to release a new version

docs/release-flow.md

@@ -2,34 +2,15 @@
 
 #### How and when the operator version is changed
 
-The single source of truth is the version number in
-[Chart.yaml](https://github.com/ydb-platform/ydb-kubernetes-operator/blob/master/deploy/ydb-operator/Chart.yaml#L18)
-file.
-
-It is incremented according to semver practices. Essentially, it is incremented every
-time any change is made into either chart or the operator code.
-
-For the contrast, changing some details of Github workflows or rewriting the docs
-does not initiate a new release.
-
-#### What the CI does
-
-When you increment the version in `Chart.yaml` and your PR is merged into master, tag
-is automatically extracted from the Chart like this:
-
-```
-"version: 0.4.22"  ->  "0.4.22"
-```
-
-If the version is new (no previous commit was tagged with this version), then:
-
-- this merge commit gets tagged with version extracted from `Chart.yaml`;
-- new docker image is built and uploaded to `cr.yandex/yc/ydb-kubernetes-operator`;
-- new chart version is uploaded to https://charts.ydb.tech.
-
-#### What if I forget to bump up the chart version?
-
-Then these changes won't get automatically tagged, new version won't be built and
-uploaded and you most likely will notice it immediately when you'll want to use an
-updated version. Then you make another PR with a chart version bump and get your
-changes rebuilt.
+The single source of truth is the changelog. 
+
+Currently, version is updated when a developer decides to release a new version by manually invoking
+`create-release-pr` workflow in Github Actions:
+
+- invoke `create-release-pr` workflow
+- `changie` tool automatically bumps the version and generates an updated CHANGELOG.md
+- if a generated `CHANGELOG.md` looks okay, just merge it
+- the `upload-artifacts` workflow will:
+    - substitute the latest version in `Chart.yaml`
+    - build artifacts (docker image and helm chart) and upload them to all configured registries
+    - create a new Github release