Add last_response_header for rate limit debugging

Author: anthony-chaudhary

sdk/diffgram/core/core.py

@@ -20,6 +20,7 @@
 
 class Project():
     default_directory: Directory
+    last_response_header: None
 
     def __init__(
             self,
@@ -225,6 +226,9 @@ def handle_errors(self,
         after this, and that fails in poor way if there is no json available.
         """
 
+        if response.headers:
+            self.last_response_header = response.headers
+
         # Default
         if response.status_code == 200:
             return