Add FHIR resolver example script (#11)

- Introduced a new script `fhir_resolver.py` that demonstrates FHIR-to-OMOP concept resolution using the OMOPHub SDK.
- The script includes examples for resolving SNOMED, ICD-10-CM, LOINC, RxNorm codes, and text-only semantic searches.
- Added functionality for direct standard lookups, non-standard code mapping, and Phoebe recommendations.
- Supports batch resolution and asynchronous usage for improved performance.

Co-authored-by: alex-omophub <sdk@omophub.com>

Author: alex-omophub