update README and logo

README.md

@@ -13,13 +13,14 @@ license_link: LICENSE
 
 The **Yi** series models are large language models trained from scratch by
 developers at [01.AI](https://01.ai/). The first public release contains two
-bilingual(English/Chinese) base models with the parameter sizes of 6B and 34B.
-Both of them are trained with 4K sequence length and can be extended to 32K
-during inference time.
+bilingual(English/Chinese) base models with the parameter sizes of 6B(`Yi-6B`)
+and 34B(`Yi-34B`). Both of them are trained with 4K sequence length and can be
+extended to 32K during inference time. The `Yi-6B-200K` and `Yi-34B-200K` are
+base model with 200K context length. 
 
 ## News
 
-- 🎯 **2023/11/05**: The base model of 'Yi-6B-200K' and 'Yi-34B-200K' with 200K context length.
+- 🎯 **2023/11/05**: The base model of `Yi-6B-200K` and `Yi-34B-200K` with 200K context length.
 - 🎯 **2023/11/02**: The base model of `Yi-6B` and `Yi-34B`.