Increase chunk_size to 1MiB (#87)

Should increase download speeds.

htmlproofer/plugin.py

@@ -152,7 +152,7 @@ def resolve_web_scheme(self, url: str) -> int:
 
             if self.config['skip_downloads'] is False:
                 # Download the entire contents as to not break previous behaviour.
-                for _ in response.iter_content(chunk_size=1024):
+                for _ in response.iter_content(chunk_size=1024 * 1024):
                     pass
 
             return response.status_code