Add password rules for bkvenergy.com

[jasontenpenny]

Added necessary rules for bkvenergy.com

Overall Checklist

• I agree to the project's Developer Certificate of Origin
• The top-level JSON objects are sorted alphabetically
• There are no open pull requests for the same update

for password-rules.json

• The given rule isn't particularly standard and obvious for password managers
• Generated passwords have been tested from this rule using the Password Rules Validation Tool
• Information has been included about the website's requirements (eg. screenshots, error messages, steps during experimentation, etc.)
• The PR isn't documenting something that would be a common practice among password managers (e.g. minimal length of 6)

URL: https://bkvenergy.com/account/register/

This website has a pretty narrow restriction on password length, which I think was the main thing preventing the auto-generated passwords from working. Created a rule that includes all the specified requirements, and test passwords are passing.