refactor(docs): move from reST to Markdown (#13)

Convert docs from reStructuredText to Markdown so that the changelog
file is compatible with Release Please.

AUTHORS.md

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+# Authors
+
+The list of contributors in alphabetical order:
+
+- [Agisilaos Kounelis](https://orcid.org/0000-0001-9312-3189)
+- [Elena Gazzarrini](https://orcid.org/0000-0001-5772-5166)
+- [Marco Donadoni](https://orcid.org/0000-0003-2922-5505)
+- [Tibor Simko](https://orcid.org/0000-0001-7202-5803)

README.md

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+# REANA Authentication Rucio
+
+[![image](https://github.com/reanahub/reana-auth-rucio/workflows/CI/badge.svg)](https://github.com/reanahub/reana-auth-rucio/actions)
+[![image](https://img.shields.io/badge/discourse-forum-blue.svg)](https://forum.reana.io)
+[![image](https://img.shields.io/github/license/reanahub/reana-auth-rucio.svg)](https://github.com/reanahub/reana-auth-rucio/blob/master/LICENSE)
+
+## About
+
+`reana-auth-rucio` provides a container image for creating the right Rucio configuration
+for REANA workflow jobs. The container image includes no additional logic or libraries,
+just the bare minimum to support Rucio. The image is configured to support authentication
+for the four experiments at CERN's Large Hadron Collider (ALICE, ATLAS, CMS, LHCb), as
+well as [ESCAPE](https://projectescape.eu/) Virtual Organization.
+
+`reana-auth-rucio` was developed for use in the [REANA](http://www.reana.io/) reusable
+research data analysis platform.
+
+## Usage
+
+You can use `reana-auth-rucio` as a base image, however it was built to be used as a
+sidecar container with the single purpose of creating the right Rucio configuration. Once
+obtained, the configuration files are shared with the main container using common
+namespaces.
+
+The end users can ask for Rucio support by means of declaring `rucio: true`. Currently,
+the container requires VOMS authentication meaning that `voms_proxy: true` has also to be
+declared, enabling the
+[reana-auth-vomsproxy](https://github.com/reanahub/reana-auth-vomsproxy) sidecar
+container.
+
+Inside the container Rucio commands can be executed, for example via:
+
+```console
+$ rucio whoami
+```
+
+## Dependencies
+
+Building the container and successfully obtaining Rucio configuration requires additional
+files present in this repository:
+
+- `files/CERN-bundle.pem` downloaded from
+  [Rucio GitLab repository](https://gitlab.cern.ch/plove/rucio/-/tree/master/etc/web);
+- `files/rucio.cfg.j2` Rucio configuration template.
+
+## Changes
+
+### Version 1.1.1 (2023-09-11)
+
+- Adds more WLCG certificates to facilitate data access to outside-CERN sites.
+
+### Version 1.1.0 (2023-08-22)
+
+- Changes Rucio client version to 1.30.0.
+- Changes installation to use fully-qualified container image names to be Podman
+  friendly.
+- Fixes EGI trustanchors installation troubles by switching to CERN CA bundles.
+
+### Version 1.0.0 (2022-10-13)
+
+- Initial release.
+
+## Development
+
+You can build the `reana-auth-rucio` image by optionally passing the build arguments
+`BASETAG` in order to specify the tag of `rucio/rucio-clients`.
+
+## More information
+
+For more information about [REANA](https://www.reana.io/) reusable research data analysis
+platform, please see [its documentation](https://docs.reana.io/).