Added .readthedocs.yaml config file

[lslezak]

Problem

• The https://yastgithubio.readthedocs.io/en/latest/ page has not been updated for almost a year! 😱
• The builds are failing, see the build log
• The error is The required .readthedocs.yaml configuration file was not found at repository's root.

Solution

• Add the required config file
• I basically reused the template from the Readthedocs documentation
• Let's see if that helps...