Add an example for user stories (#399)

Add an example for user stories and fix some typo

Add a new section, user story in the docs, to collect user stories of
llvm-ascend, also add an example and the issue template to collect user
story

Signed-off-by: Zhenyu Zheng <zheng.zhenyu@outlook.com>

docs/source/user_stories/example.md

@@ -0,0 +1,15 @@
+# xxx project uses Ascend vLLM, gain 200% performance enhancement of inference.
+
+## About / Introduction
+Draft content
+
+## The Business Challenge
+Our goal is to ...
+
+## Solving challenges with vLLM Ascend
+vLLM Ascend helped us ...
+
+## Benefits using vLLM Ascend
+
+## Learn more
+more info about this case