[Doc] Add container image save/load FAQ for offline environments (#2347)

### What this PR does / why we need it?

Add Docker export/import guide for air-gapped environments

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?

NA

- vLLM version: v0.10.0
- vLLM main:
vllm-project/vllm@d16aa3d

Signed-off-by: QwertyJack <[email protected]>

Author: QwertyJack

docs/source/faqs.md

@@ -36,6 +36,33 @@ TAG=v0.7.3rc2
 docker pull m.daocloud.io/quay.io/ascend/vllm-ascend:$TAG
 ```
 
+#### Load Docker Images for offline environment
+If you want to use container image for offline environments (no internet connection), you need to download container image in a environment with internet access:
+
+**Exporting Docker images:**
+
+```{code-block} bash
+   :substitutions:
+# Pull the image on a machine with internet access
+TAG=|vllm_ascend_version|
+docker pull quay.io/ascend/vllm-ascend:$TAG
+
+# Export the image to a tar file and compress to tar.gz
+docker save quay.io/ascend/vllm-ascend:$TAG | gzip > vllm-ascend-$TAG.tar.gz
+```
+
+**Importing Docker images in environment without internet access:**
+
+```{code-block} bash
+   :substitutions:
+# Transfer the tar/tar.gz file to the offline environment and load it
+TAG=|vllm_ascend_version|
+docker load -i vllm-ascend-$TAG.tar.gz
+
+# Verify the image is loaded
+docker images | grep vllm-ascend
+```
+
 ### 3. What models does vllm-ascend supports?
 
 Find more details [<u>here</u>](https://vllm-ascend.readthedocs.io/en/latest/user_guide/support_matrix/supported_models.html).