[online_image] Add JPEG support to online_image (#8127)

Co-authored-by: Jimmy Hedman <jimmy.hedman@gmail.com>
Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: Rodrigo Martín <contact@rodrigomartin.dev>
Co-authored-by: Clyde Stubbs <2366188+clydebarrow@users.noreply.github.com>

esphome/components/online_image/image_decoder.h

@@ -106,6 +106,8 @@ class DownloadBuffer {
 
   void reset() { this->unread_ = 0; }
 
+  size_t resize(size_t size);
+
  protected:
   RAMAllocator<uint8_t> allocator_{};
   uint8_t *buffer_;