Add documentation to https://docs.hedera.com/

[piotrswierzy]

• Rise a PR to: https://github.com/hashgraph/hedera-docs
  • example PR for new docs: https://github.com/hashgraph/hedera-docs/pull/492/changes
• Prepare a gap report ("Visual") showcasing what hedera functionality are supported