add offset param & email extraction (#51)

* add offset param

* [enh]: extract emails

src/tests/test_ziprecruiter.py

@@ -1,4 +1,5 @@
 from ..jobspy import scrape_jobs
+import pandas as pd
 
 
 def test_ziprecruiter():
@@ -7,4 +8,4 @@ def test_ziprecruiter():
         search_term="software engineer",
     )
 
-    assert result is not None and result.errors.empty is True
+    assert isinstance(result, pd.DataFrame) and not result.empty, "Result should be a non-empty DataFrame"