JOSS paper comments

[jsheunis]

Issue related to JOSS review: openjournals/joss-reviews#4248

The current version of the JOSS paper is well written and clearly explains the need and functionality of CMP3. I have a few comments:

• While reading through the paper content, I adapted the wording slightly in a few places. These are (in my opinion) minor improvements, and you can use your discretion to decide whether or not to include these changes. I'll submit a small PR shortly.
• The JOSS guidelines state that the paper should have "A summary describing the high-level functionality and purpose of the software for a diverse, non-specialist audience". At the moment, the summary section makes out the bulk of the paper, and I consider much of it to be quite detailed and specialist. I don't think this content is a problem though, just that I'm missing a shorter summary for a diverse, non-specialist audience. Perhaps a new paragraph could be included to serve as such a summary, while the current Summary section could be renamed to Functionality (or something similar). That is if you (and the JOSS editors) agree that this is indeed a useful approach.
• The Mention section's title seems a bit out of context, perhaps rename it to Software use or Ongoing research or Community impact, or something along those lines.