Should be imperative mood, there is no such thing as imperative tense

https://github.com/commitizen/cz-conventional-changelog/blob/d4bf98e59b0d24e18876945546181ada5e2f7448/engine.js#L64

Just a nitpick, but it would be an improvement to re-word this message, perhaps with a brief example in the line. At the very least, this should be replaced with "mood" instead of "tense". I like how this example explains the intent of this type of commit message (https://git.kernel.org/pub/scm/git/git.git/tree/Documentation/SubmittingPatches):

> Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
> instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
> to do frotz", as if you are giving orders to the codebase to change
> its behavior. Try to make sure your explanation can be understood
> without external resources. Instead of giving a URL to a mailing list
> archive, summarize the relevant points of the discussion.