Nowadays it is only possible to transition JIRA issues, but you cannot create JIRA issues.

A suggestion is to add a command like #create and the next thing in the commit message should be the JIRA project key, and also add a command like #type where you can specify if it's a bug, or improvement, etc.
Example:

This is the commit message. #create JRA #type bug #comment this is a comment in JIRA side

Of course, the JIRA issue creation screen should be the default one, without any custom fields.