Improve usages additional features added

• Bump versions + add example of code
• Moving to kotlin 1.5.0.
• Improving tests
• Adding nested items
• Structure the MdElements
• Adding sentence as a text of link. Integrating short Link References
• Adding readme, settings, tests, gradle -> 7.0
• Updating readme with latest release version

Initial release

Minimal implementation of markdown generation. The interfaces are prone to further changes.