Improve model card: update pipeline tag and add relevant tags

This PR improves the model card for OS-Genesis-7B-AW by:

- Updating the `pipeline_tag` from `any-to-any` to `image-text-to-text`, which more accurately reflects the model's functionality (taking image and text inputs to produce text outputs) and ensures it appears in the correct filtering category on the Hub (https://huggingface.co/models?pipeline_tag=image-text-to-text).
- Adding relevant `tags` such as `gui-agent`, `web-agent`, `mobile-agent`, `qwen2-vl`, and `multimodal` to further describe the model's domain, application, and architecture for better discoverability.
- No changes were made to the paper link in the content, adhering to the instruction that an existing arXiv link does not need to be replaced.

README.md

@@ -2,7 +2,13 @@
 base_model: Qwen/Qwen2-VL-7B-Instruct
 library_name: transformers
 license: apache-2.0
-pipeline_tag: any-to-any
+pipeline_tag: image-text-to-text
+tags:
+  - gui-agent
+  - web-agent
+  - mobile-agent
+  - qwen2-vl
+  - multimodal
 ---
 
 # OS-Genesis: Automating GUI Agent Trajectory Construction via Reverse Task Synthesis