No documentation about what issues NullArgumentForNonNullParameter detects

[The documentation page for `NullArgumentForNonNullParameter`](https://errorprone.info/bugpattern/NullArgumentForNonNullParameter) is essentially empty. It only says how to suppress.

The reason that I came to this documetnation page is that I wanted to understand the difference between `NullArgumentForNonNullParameter` and [the Error Prone plugin `NullAway`](https://github.com/uber/NullAway). The other place I looked is the GitHub repo for `NullAway`, but [it never mentions `NullArgumentForNonNullParameter`](https://github.com/search?q=repo%3Auber%2FNullAway%20NullArgumentForNonNullParameter&type=issues).