Fix example command for adding a version

[dbeatty10]

Version

$ pip show dbt-meshify 
Name: dbt-meshify
Version: 0.5.2

Current behavior

$ dbt-meshify version --select customers             

Usage: dbt-meshify [OPTIONS] COMMAND [ARGS]...
Try 'dbt-meshify --help' for help.

Error: No such command 'version'.

Expected behavior

$ dbt-meshify operation add-version --select customers

Add version 1 to the customers model where none existed previously.

[dbeatty10]

I think I had an out-dated version of dbt-meshify in my virtual environment.

After making certain I had the latest version of dbt-meshify working in my local environment, the example command did indeed work, so I'm closing this issue.

But opened #200 instead, 'cause that would have helped me identify the issue with my environment faster.