docs: Add viztracer command for testing targets (#1925)

* Add viztracer command for testing targets

When it comes to testing targets it took me a long while to work out I could use the `--input` switch to pass a file of records to the target rather than trying to work out how to run `viztracer` on a command containing a pipe 🤯. If the added line can be proven to work by a reviewer and it's OK to be added to the documentation then it would have saved me heaps of time yesterday 😄

* Update poetry command

---------

Co-authored-by: Edgar Ramírez Mondragón <edgar@meltano.com>

docs/dev_guide.md

@@ -257,13 +257,14 @@ We've had success using [`viztracer`](https://github.com/gaogaotiantian/viztrace
 You can start doing the same in your package. Start by installing `viztracer`.
 
 ```console
-$ poetry add --dev viztracer
+$ poetry add --group dev viztracer
 ```
 
 Then simply run your package's CLI as normal, preceded by the `viztracer` command
 
 ```console
 $ poetry run viztracer my-tap
+$ poetry run viztracer -- my-target --config=config.json --input=messages.json
 ```
 
 That command will produce a `result.json` file which you can explore with the `vizviewer` tool.