Add RELEASING.md with necessary instructions

RELEASING.md

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+# Releasing new version
+
+## Step-by-step
+
+In order to release a new version, there are several steps that must happen:
+
+ 0. make sure all issues (in GitHub and in JIRA) targeted to the version are resolved
+ 1. create a pull request in which you change the [version string](https://github.com/modcluster/mod_proxy_cluster/blob/main/native/include/mod_proxy_cluster.h#L21) according to the format described in [another section](#version-naming-conventions)
+ 2. get review and merge the pull request
+ 3. release the version through GitHub release functionality with a new tag corresponding to the version string from
+ the pull request (create the tag during the release through the release dialog)
+ 4. mark the corresponding version[^1] released in [JIRA](https://issues.redhat.com/projects/MODCLUSTER?release-page) as well
+
+
+## Version naming conventions
+
+Version string must have the following format:
+
+* `major.minor.micro.Dev`
+* `major.minor.micro.Alpha<number>`
+* `major.minor.micro.Beta<number>`
+* `major.minor.micro.CR<number>`
+* `major.minor.micro.Final`
+
+where `<number>` is a mandatory numerical value starting from `1`. Any version marked `Final` must
+not have a number. If there is any issue with such a version, just increase a micro version and go
+through the process again.
+
+Versions in between of `x.y.z.Final` and next `a.b.c.Alpha1` will be called `a.b.c.Dev`.
+
+[^1]: The corresponding version within the JIRA project has `native-` prefix. For example version `2.0.0.Final` in this repository will be `native-2.0.0.Final` in the JIRA project.