Convert the official readme into markdown for better rendering support

Reference : https://github.com/miyakogi/m2r

added doing label

assigned to @christian_eichenberger and unassigned @mohanty

mentioned in commit bbd6d9f3

mentioned in merge request !205 (merged)

changed milestone to %v3

closed via merge request !205 (merged)

mentioned in commit d4cdf9c3