Fix Bing Provider, Add Account Support for Meta AI

Use default headers in OpenaiChat

g4f/gui/server/api.py

@@ -7,6 +7,7 @@ from typing import Iterator
 from g4f import version, models
 from g4f import get_last_provider, ChatCompletion
 from g4f.errors import VersionNotFoundError
+from g4f.image import ImagePreview
 from g4f.Provider import ProviderType, __providers__, __map__
 from g4f.providers.base_provider import ProviderModelMixin, FinishReason
 from g4f.providers.conversation import BaseConversation
@@ -146,6 +147,8 @@ class Api():
                 elif isinstance(chunk, Exception):
                     logging.exception(chunk)
                     yield self._format_json("message", get_error_message(chunk))
+                elif isinstance(chunk, ImagePreview):
+                    yield self._format_json("preview", chunk.to_string())
                 elif not isinstance(chunk, FinishReason):
                     yield self._format_json("content", str(chunk))
         except Exception as e: