Liminal Network API Example client code

Our API is documented at https://www.liminalnetwork.com/ .

There, we reference doc_client.py, which is in this repository as src/doc_client.py . Most functions in doc_client.py are defined in other files, referenced in the "Imported functions" section of our extended client documentation: https://github.com/liminalnetwork/sample/blob/main/docs/src.doc_client.md