Compare against softwarecite-mentions and add some notes to README or Related Work

[jyoung3131]

Our understanding is that tools like software-mentions do a more complicated meta-analysis of software usage and citation, which is a bit different than the focus of SoftwareCitationAuditor, which focuses on recommending missing software citations. That said, it would be good to run some samples with both tools and understand the differences so that we can better inform users.

https://github.com/softcite/software-mentions