CHANGELOG verb tenses are inconsistent

The CHANGELOG has a mix of present, past, and imperative tenses for the first verb ... e.g., Update, Updating, and Updated can be seen. As I'm sure that you're aware, [git suggests using imperative for commit messages](https://www.danclarke.com/git-tense). I agree with the author of the blog post that it really doesn't matter as long as it's consistently followed. It would be helpful to add some directions to the CHANGELOG to tell people which tense to use.

Start with the CHANGELOG and review the existing first-verb tenses, including Update, Updating, and Updated. Add guidance that specifies one consistent tense for future entries, then verify that the directions are clear and match the chosen convention.

Written by the indexing model from the issue text.