Add 'SHOW VERSION' to document (#11082)

### What problem does this PR solve?

As title

### Type of change

- [x] Documentation Update

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

docs/guides/manage_users_and_services.md

@@ -72,7 +72,7 @@ Commands are case-insensitive and must be terminated with a semicolon(;).
 
 ### Service manage commands
 
- `LIST SERVICES;`
+`LIST SERVICES;`
 
 - Lists all available services within the RAGFlow system.
 
@@ -83,6 +83,11 @@ Commands are case-insensitive and must be terminated with a semicolon(;).
 - Shows detailed status information for the service identified by **id**.
 - [Example](#example-show-service)
 
+`SHOW VERSION;`
+
+- Shows RAGFlow version.
+- [Example](#example-show-version)
+
 ### User Management Commands
 
 `LIST USERS;`
@@ -232,6 +237,18 @@ Service redis is alive. Detail:
 | 0               | 2                 | 1                         | 10.41                   | 7.2.4         | standalone  | 10446                    | 30.84G              | 1.10M       |
 +-----------------+-------------------+---------------------------+-------------------------+---------------+-------------+--------------------------+---------------------+-------------+
 ```
+<span id="example-show-version"></span>
+
+- Show RAGFlow version
+
+```
+admin> show version;
++-----------------------+
+| version               |
++-----------------------+
+| v0.21.0-241-gc6cf58d5 |
++-----------------------+
+```
 
 <span id="example-list-users"></span>