Generate plausible/possible usernames

Probably as a separate feature/function:

```
getUsernames("John Doe") => [ j.doe, jdoe, doejohn ]
```

Start by locating the module entry point and any existing name-generation functions, then define the proposed getUsernames("John Doe") behavior from the issue example. Done means the function returns plausible username variants for a human name and the project’s existing checks pass; no test file is named in the issue.

Written by the indexing model from the issue text.