docs(versioning): adding dokka versioning plugin

[DariusIMP]

Overview

This PR introduces the dokka versioning plugin (see https://kotlin.github.io/dokka/1.4.30/user_guide/versioning/versioning/).

This allows to display a dropdown menu on the documentation site with the old versions:

How it works

The plugin is configured in such a way that in order to be able to build the documentation with versioning, we need to

1. Have the latest docs version under /docs
2. Have the older documentation versions under /docs/older.

When those requirements are met, then when runing

gradle dokkaHtml

an html site with the documentation is generated which contains the older versions.

[github-actions]

PR missing one of the required labels: {'internal', 'new feature', 'breaking-change', 'documentation', 'enhancement', 'dependencies', 'bug'}