[Doc] Add a release guide and an empty ChangeLog file

The release guide is partially based on guides in
pmem/pmemkv and pmem/pmdk repos.

Author: lukaszstolarczuk

ChangeLog

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+<day of week> <month> <day> 2024 <Author> <[email protected]>
+
+	* Version 0.1.0
+
+	This is the first release of Unified Memory Framework project.
+
+	...

RELEASE_STEPS.md

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+## UMF Release Steps
+
+This document contains all the steps required to make a new release of UMF.
+
+As a helper, we use in this guide these 2 variables:
+```bash
+  set $VERSION = current full version (e.g., 0.1.0-rc1) # -rc1 included just as an example
+  set $VER = current major+minor only version (e.g., 0.1)
+```
+
+## Make a release locally
+
+Before doing the final release it's recommended to prepare a pre-release version - a "release candidate"
+(or "rc" in short). This requires adding, e.g., `-rc1` to the VERSION string. When all tests and checks
+end properly, you can follow up with the final release. If any fix is required, it should be included in
+another rc package (e.g., `-rc2`).
+
+To do a release:
+- Add an entry to ChangeLog, remember to change the day of the week in the release date
+  - For major releases mention API and ABI compatibility with the previous release
+- Update project's version in top-level CMakeLists.txt
+- Commit these changes and tag the release:
+  - git commit -a -S -m "$VERSION release"
+  - git tag -a -s -m "Version $VERSION" $VERSION
+
+- Now, update project's version in top-level CMakeLists.txt to "$VERSION-devel"
+  - This implies that the version is ahead of the previous tag and it's a development build
+  - This way only one commit (the tagged one) will introduce itself as "$VERSION" in CMake
+- For major/minor releases add a new, empty ChangeLog entry (for $VERSION+1)
+- Commit these changes:
+  - git commit -a -m "Update version to devel"
+
+- For major/minor release:
+  - If stable branch for this release is not created and it's required, create it:
+    - git checkout -b v$VER.x (e.g., `v0.1.x`)
+
+## Publish changes
+
+As patch releases should be done on the stable branches, pushing tags differ a little.
+
+For major/minor release:
+  - Push main:
+    - git push upstream HEAD:main $VERSION
+  - And, if stable branch was also created, push it to upstream:
+    - git checkout v$VER.x
+    - git push upstream HEAD:v$VER.x
+- for patch release:
+  - git push upstream HEAD:v$VER.x $VERSION
+
+## Announce release
+
+To make the release official:
+- go to [GitHub's releases tab](https://github.com/oneapi-src/unified-memory-framework/releases/new):
+  - tag version: $VERSION, release title: UMF $VERSION, description: copy entry from ChangeLog and format it with no tabs and no characters limit in line
+- announce the release, if needed
+
+## More information
+
+To assure the community that the release is a valid package from UMF maintainers, it's recommended to sign the release
+commit and the tag (`-S`/`-s` parameters in commands above). If you require to generate a GPG key follow
+[these steps](https://docs.github.com/en/authentication/managing-commit-signature-verification/generating-a-new-gpg-key).
+After that you'd also have to add this new key to your GitHub account - please do the steps in
+[this guide](https://docs.github.com/en/authentication/managing-commit-signature-verification/telling-git-about-your-signing-key).