Add filter for author search by date of birth and date of death

### Proposal

Add a new filter to the author search functionality that allows users to refine their search by the author's date of birth and/or date of death. This feature would improve the search experience for users looking for authors from specific time periods.

### **Problem(s) the proposal addresses:**
Currently, the author search functionality lacks the ability to filter results by date of birth and date of death. This limitation makes it challenging for users who are not looking for a specific author but are instead interested in discovering authors from a particular historical period.

### **Predicted Impact:**
By adding filters for date of birth and date of death, users will be able to:
1. **Improve search precision** – Users can target specific authors by limiting the date range, making the search results more accurate and efficient.
2. **Enhance user experience** – Researchers, historians, and others who focus on specific historical periods or wish to compare authors by generation will find this feature particularly useful.

### **Other context:**
- The filters should allow for ranges (e.g., authors born between 1900-1950) and handle incomplete data (e.g., only known birth dates or unknown death dates).

- It appears that the data is already available and can be filtered :
```json
{
"alternate_names": [
"Bogan, Louise, 1897-1970."
],
"birth_date": "11 August 1897",
"death_date": "4 February 1970",
"key": "OL446220A",
"name": "Louise Bogan",
"top_subjects": [
"20th century",
"American poetry",
"Louise Bogan (1897-1970)",
"United States",
"Modern Literature",
"History and criticism",
"Fiction",
"American Authors",
"short stories",
"hanging"
],
"top_work": "Achievement in American poetry",
"type": "author",
"work_count": 64,
"_version_": 1796710810956857300
}