Add GET endpoint for /library

endpoints/library.get.py

@@ -1,5 +1,5 @@
-# Entity: Book
-
+# Entity: Book, Author
+```python
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.orm import Session
 from typing import List
@@ -15,4 +15,5 @@ async def get_books_by_authors(
     db: Session = Depends(get_db)
 ):
     books = db.query(Book).join(Author).all()
-    return books
+    return books
+```