Merge pull request #43 from robberwick/rtd-readme

docs: add RTD docs link to readme

README.md

@@ -85,4 +85,6 @@ logbook_data = client.logbook(patient_identifier=patient)
 print(f"logbook data: ({len(logbook_data)} entries)")
 for measurement in logbook_data:
     print(f"{measurement.value} {measurement.timestamp} {measurement.factory_timestamp}")
-```
+```
+
+For full documentation, please refer to the [API documentation](https://pylibrelinkup.readthedocs.io/en/latest/).