Add releasing.md file

Signed-off-by: Sayali Gaikawad <[email protected]>

RELEASING.md

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+- [Overview](#overview)
+- [Branching](#branching)
+  - [Release Branching](#release-branching)
+  - [Feature Branches](#feature-branches)
+- [Release Labels](#release-labels)
+- [Releasing](#releasing)
+
+## Overview
+
+This document explains the release strategy for artifacts in this organization.
+
+## Branching
+
+### Release Branching
+
+Given the current major release of 1.0, projects in this organization maintain the following active branches.
+
+- **main**: The next _major_ release. This is the branch where all merges take place and code moves fast.
+- **1.x**: The next _minor_ release. Once a change is merged into `main`, decide whether to backport it to `1.x`.
+- **1.0**: The _current_ release. In between minor releases, only hotfixes (e.g. security) are backported to `1.0`.
+
+Label PRs with the next major version label (e.g. `2.0.0`) and merge changes into `main`. Label PRs that you believe need to be backported as `1.x` and `1.0`. Backport PRs by checking out the versioned branch, cherry-pick changes and open a PR against each target backport branch.
+
+### Feature Branches
+
+Do not create branches in the upstream repo, use your fork, for the exception of long lasting feature branches that require active collaboration from multiple developers. Name feature branches `feature/<thing>`. Once the work is merged to `main`, please make sure to delete the feature branch.
+
+## Release Labels
+
+Repositories create consistent release labels, such as `v1.0.0`, `v1.1.0` and `v2.0.0`, as well as `patch` and `backport`. Use release labels to target an issue or a PR for a given release.
+
+## Releasing
+
+The release process is standard across repositories in this org and is run by a release manager volunteering from amongst [maintainers](MAINTAINERS.md).
+
+1. Create a tag, e.g. v2.1.0, and push it to the GitHub repo.
+1. The [release-drafter.yml](.github/workflows/release-drafter.yml) will be automatically kicked off and a draft release will be created.
+1. This draft release triggers the [jenkins release workflow](https://build.ci.opensearch.org/job/oui-release/) as a result of which OUI is released on [npmjs](https://www.npmjs.com/package/@opensearch-project/oui).
+1. Once the above release workflow is successful, the drafted release on GitHub is published automatically.
+1. Increment "version" in package.json to the next patch release, e.g. v2.1.1. See [example](https://github.com/opensearch-project/opensearch-js/pull/318)