docs: add docs publishing information (keptn#949)

docs/README.md

@@ -35,3 +35,56 @@ To use the auto-fix option, run:
 ```shell
 make markdownlint-fix
 ```
+
+## Publishing
+
+We are using Netlify to publish our pages.
+There are 3 different types of publication:
+
+1. pull request previews
+2. development documentation aka staging (build of `main` branch) - [link](https://main.lifecycle-test.keptn.sh)
+3. official documentation aka production (build of `page` branch) - [link](https://lifecycle-test.keptn.sh)
+
+Within the navigation bar, we do have version links pointing to the different publications - if it makes sense.
+For example, we are not linking from development and production to pull request previews.
+
+### Pull request preview
+
+- build: on each pull request with documentation changes
+- build-environment: development
+- config folder: [_default](./config/_default/)
+
+The pull request preview will be generated if documentation files have been touched - this is configured in the [netlify.toml](../netlify.toml).
+
+This preview should help contributors to inspect their changes within our usual page release.
+Furthermore, it allows reviewers to inspect the rendered documentation without building it on their own.
+
+### Development page
+
+- build: on each push to `main` with documentation changes
+- build-environment: main
+- config folder: [main](./config/staging/)
+
+This page reflects the current development status of the documentation.
+It will be built regularly and can be easily accessed.
+
+It should allow bleeding-edge users and contributors to see the current state and help with debugging etc.
+
+### Official documentation
+
+- build: on each push to `page` with documentation changes
+- build-environment: production
+- config folder: [production](./config/production/)
+
+This documentation set contains all released versions of KLT and is stored in an orphaned branch called `page`.
+
+Each version has its own `docs` folder named `docs-<version>`.
+Except for the latest version which will be within the `docs` folder.
+
+Each version-specific documentation contains a `version` file containing the version string.
+This is important so we do know which version it contains - specifically important for `docs` of the latest version.
+
+`Docsy` offers a mechanism to build a version menu based on Hugo's configuration.
+We extended this mechanism and enhanced it with a check for directories starting with `docs` and containing a `version` file.
+For more details inspect the [layout file with adaptions](layouts/partials/navbar-version-selector.html).
+This way we do not need to adapt the configuration all the time we are releasing a new version.