Support repositories using format RST for changelog

[ckunki]

Jave developers of the integration team are using markdown for documentation incl. file changelog and release notes in files change_1.2.2.md. Python developers would prefer to use reStructured text (RST).

• Does RD need to support different format for changes files, too?
• See Sphinx
• See example integration-test-docker-environment (ITDE)

AC

1. RD detects preferred format for the affected files: either markdown or RST
2. RD supports appropriate suffixes of file names, e.g. .md and .rst
3. RD supports resp. format inside the file to detect the information RD needs for validating and creating releases