There is a clear invitation to contribute to the software, although no detail on the preferred method of or type of contributions is given (eg opening issues, editing docs, PRs, etc).
(@kbarnhart will improve the contribution guidelines to provide more detail regarding the preferred method of contribution and the type of contributions that are welcome).
In a JOSS review @sgrieve points out:
(@kbarnhart will improve the contribution guidelines to provide more detail regarding the preferred method of contribution and the type of contributions that are welcome).