[Doc] Update doc to work with release (#85)

1. Update CANN image name
2. Add pta install step
3. update vllm-ascend docker image name to ghcr
4. update quick_start to use vllm-ascend image directly.
5. fix `note` style

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

docs/source/conf.py

@@ -65,7 +65,10 @@ myst_substitutions = {
     'vllm_version': 'main',
     # the branch of vllm-ascend, used in vllm-ascend clone and image tag
     # such as 'main', 'v0.7.1-dev', 'v0.7.1rc1'
-    'vllm_ascend_version': 'main'
+    'vllm_ascend_version': 'main',
+    # the newest release version of vllm, used in quick start or container image tag.
+    # This value should be updated when cut down release.
+    'vllm_newest_release_version': "v0.7.1.rc1",
 }
 
 # Add any paths that contain templates here, relative to this directory.