docs(API): create reference documentation for API using Open RPC standard

[BrunoCampana]

Objective:

• Document the API exposed by wallet applications to communicate with dApps on the Hathor platform.
• API type: JSON-RPC 2.0.
• API documented using the Open RPC standard.
• API documented in the openrpc.json file.
• The file should be used to automatically generate documentation on the Hathor docs website, similar to how it is already done with the full node and headless APIs.
• The final format that will be used is still being defined.
• For now, the following format can be used as a minimum standard to be used, but it should still improve the UI/UX:

https://beta-test.docs.hathor.network/references/dapps/rpc-api/htr_getBalance

Only one file to be reviewed: openrpc.json