[Docs] optimize and supplement docs system (#86)

Signed-off-by: Gaohan123 <gaohan19@huawei.com>

docs/usage/faq.md

@@ -0,0 +1,13 @@
+# Frequently Asked Questions
+
+> Q: How many chips do I need to infer a model in vLLM-Omni?
+
+A: Now, we support natively disaggregated deployment for different model stages within a model. There is a restriction that one chip can only has one AutoRegressive model stage. This is because the unified KV cache management of vLLM. Stages of other types can coexist with in a chip. The restriction will be resolved in later version.
+
+> Q: When trying to run examples, I encounter error about backend of librosa or soundfile. How to solve it?
+
+A: If you encounter error about backend of librosa, try to install ffmpeg with command below.
+```
+sudo apt update
+sudo apt install ffmpeg
+```